diff --git a/.gitignore b/.gitignore
index ed955cc9..b8003009 100644
--- a/.gitignore
+++ b/.gitignore
@@ -79,6 +79,7 @@ heapprt
 if
 if-jl
 if-strict
+inc/*.h
 incunabulum
 junk
 ll19
@@ -104,7 +105,6 @@ pipecircle
 piped-merge-sort
 pipeline
 pipesize
-posixver.h
 pthread-37
 pthread-?
 q7
diff --git a/etc/README.md b/etc/README.md
new file mode 100644
index 00000000..357c3d42
--- /dev/null
+++ b/etc/README.md
@@ -0,0 +1,3 @@
+# Miscellaneous directory
+
+Initially, to hold soq.mk, the common makefile.  Other files if needed.
diff --git a/etc/soq.mk b/etc/soq.mk
new file mode 100644
index 00000000..95972b6c
--- /dev/null
+++ b/etc/soq.mk
@@ -0,0 +1,36 @@
+# Makefile fragment for SOQ (aka Himalayan-Yeti) GitHub Project
+#
+# Use: include ../../etc/soq.mk in a per-directory source file
+
+BASEDIR = ../..
+
+LIBBASE = soq
+LIBNAME = lib${LIBBASE}.a
+LIBDIR  = ${BASEDIR}/lib
+HDRDIR  = ${BASEDIR}/inc
+LIBPATH = ${LIBDIR}/${LIBNAME}
+
+CC     = gcc
+SFLAGS = -std=c11
+WFLAG1 = -Wall
+WFLAG2 = -Wextra
+WFLAG3 = -Werror
+WFLAG4 = -Wmissing-prototypes
+WFLAG5 = -Wstrict-prototypes
+WFLAG6 = #-Wold-style-declaration # Strict GCC only (not clang, it would seem).
+WFLAG7 = -Wold-style-definition
+WFLAGS = ${WFLAG1} ${WFLAG2} ${WFLAG3} ${WFLAG4} ${WFLAG5} ${WFLAG6} ${WFLAG7}
+OFLAGS = -O3
+GFLAGS = -g
+UFLAGS = # Set on command line
+IFLAGS = -I${BASEDIR}/inc
+
+CFLAGS = ${SFLAGS} ${OFLAGS} ${GFLAGS} ${WFLAGS} ${UFLAGS} ${IFLAGS}
+
+LDFLAGS = -L${BASEDIR}/lib
+LDLIBS  = -lsoq
+
+DEBRIS = core a.out *~ *.o
+RM_FR  = rm -fr
+RM_F   = rm -f
+
diff --git a/inc/README.md b/inc/README.md
new file mode 100644
index 00000000..eee68e3d
--- /dev/null
+++ b/inc/README.md
@@ -0,0 +1,8 @@
+# Header directory
+
+I use 3-letter directories for src, bin, etc, tmp, lib — I've never seen a good reason not to use inc rather than include.
+
+This directory contains 'released' headers.
+Headers from the library source directory are installed here when they're ready for general use.
+
+The directory should be ignored apart from the README.md file.
diff --git a/lib/README.md b/lib/README.md
new file mode 100644
index 00000000..5be9fb19
--- /dev/null
+++ b/lib/README.md
@@ -0,0 +1,6 @@
+# Library directory
+
+Apart from the README.md file, this is a destination for compiled libraries.
+There shouldn't be any source code in here.
+
+The directory content should be ignored except for the README.md file.
diff --git a/src/README.md b/src/README.md
new file mode 100644
index 00000000..64d0c228
--- /dev/null
+++ b/src/README.md
@@ -0,0 +1,5 @@
+# Source directory
+
+Contains other directories, a makefile, and this README.
+
+Should not normally contain any other files.
diff --git a/src/lib/README.md b/src/lib/README.md
new file mode 100644
index 00000000..ae2658a4
--- /dev/null
+++ b/src/lib/README.md
@@ -0,0 +1,6 @@
+# Library source directory
+
+This is the source directory for library code which is compiled into the SOQ library.
+
+Most of this will be copies of code from main computers with (under protest) history missing.
+Also RCS markers will be removed after an initial commit.
diff --git a/src/lib/gcd.c b/src/lib/gcd.c
new file mode 100644
index 00000000..dde2b6f0
--- /dev/null
+++ b/src/lib/gcd.c
@@ -0,0 +1,119 @@
+/*
+@(#)File:           gcd.c
+@(#)Purpose:        Implement Greatest Common Divisor for two integers
+@(#)Author:         J Leffler
+@(#)Copyright:      (C) JLSS 1993,1997,2000,2005,2012,2015-16
+@(#)Derivation:     gcd.c,v 1.7 2015/06/02 03:05:40
+*/
+
+/*TABSTOP=4*/
+
+#include "gcd.h"
+
+int gcd(int x, int y)
+{
+    int r;
+
+    if (x <= 0 || y <= 0)
+        return(0);
+
+    while ((r = x % y) != 0)
+    {
+        x = y;
+        y = r;
+    }
+    return(y);
+}
+
+unsigned long long gcd_ull(unsigned long long x, unsigned long long y)
+{
+    unsigned long long r;
+
+    if (x == 0 || y == 0)
+        return(0);
+
+    while ((r = x % y) != 0)
+    {
+        x = y;
+        y = r;
+    }
+    return(y);
+}
+
+#if defined(TEST)
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define DIM(x)  (sizeof(x)/sizeof(*(x)))
+
+typedef struct gcd_test
+{
+    int     x;
+    int     y;
+    int     r;
+} gcd_test;
+
+static gcd_test gcd_list[] =
+{
+    { 0, 1, 0 },
+    { 1, 1, 1 },
+    { 2, 1, 1 },
+    { 3, 1, 1 },
+    { 3, 2, 1 },
+    { 4, 2, 2 },
+    { 8, 2, 2 },
+    { 16, 3, 1 },
+    { 16, 4, 4 },
+    { 16, 6, 2 },
+    { 16, 12, 4 },
+    { 4795615, 2310, 55 },
+};
+
+typedef unsigned long long ULL;
+
+static size_t test_gcd(int x, int y, int z)
+{
+    size_t f = 0;
+    int r = gcd(x, y);
+
+    if (r != z)
+        f = 1;
+    printf("%s GCD(%7d, %7d) = %7d (%7d expected)\n",
+            (r == z) ? "PASS" : "FAIL", x, y, r, z);
+    return(f);
+}
+
+static size_t test_gcd_ull(unsigned long long x, unsigned long long y, unsigned long long z)
+{
+    size_t f = 0;
+    unsigned long long r = gcd_ull(x, y);
+
+    if (r != z)
+        f = 1;
+    printf("%s GCD(%7lld, %7lld) = %7lld (%7lld expected)\n",
+            (r == z) ? "PASS" : "FAIL", x, y, r, z);
+    return(f);
+}
+
+int main(void)
+{
+    size_t i;
+    size_t n = DIM(gcd_list);
+    size_t f = 0;
+
+    for (i = 0; i < n; i++)
+    {
+        f += test_gcd(gcd_list[i].x, gcd_list[i].y, gcd_list[i].r);
+        f += test_gcd(gcd_list[i].y, gcd_list[i].x, gcd_list[i].r);
+        f += test_gcd_ull((ULL)gcd_list[i].x, (ULL)gcd_list[i].y, (ULL)gcd_list[i].r);
+        f += test_gcd_ull((ULL)gcd_list[i].y, (ULL)gcd_list[i].x, (ULL)gcd_list[i].r);
+    }
+    if (f != 0)
+        printf("*** FAILED *** (%lu tests out of %lu)\n", (unsigned long)f, (unsigned long)(2 * n));
+    else
+        printf("=== PASSED === (%lu tests)\n", (unsigned long)(2 * n));
+    return((f == 0) ? EXIT_SUCCESS : EXIT_FAILURE);
+}
+
+#endif /* TEST */
diff --git a/src/lib/gcd.h b/src/lib/gcd.h
new file mode 100644
index 00000000..84b60ea8
--- /dev/null
+++ b/src/lib/gcd.h
@@ -0,0 +1,15 @@
+/*
+@(#)File:           gcd.h
+@(#)Purpose:        GCD - Greatest Common Denominator
+@(#)Author:         J Leffler
+@(#)Copyright:      (C) JLSS 2005,2008,2012,2016
+@(#)Derivation:     gcd.h,v 1.4 2012/06/29 15:25:57
+*/
+
+#ifndef JLSS_ID_GCD_H
+#define JLSS_ID_GCD_H
+
+extern int gcd(int x, int y);
+extern unsigned long long gcd_ull(unsigned long long x, unsigned long long y);
+
+#endif /* JLSS_ID_GCD_H */
diff --git a/src/lib/makefile b/src/lib/makefile
new file mode 100644
index 00000000..b786f484
--- /dev/null
+++ b/src/lib/makefile
@@ -0,0 +1,28 @@
+# Makefile for SOQ library
+
+include ../../etc/soq.mk
+
+CP      = cp
+CPFLAGS = -fp
+
+FILES.c = \
+	gcd.c \
+	stderr.c
+
+FILES.o = ${FILES.c:.c=.o}
+FILES.h = ${FILES.c:.c=.h}
+
+all: ${LIBNAME} ${FILES.h}
+
+${LIBNAME}:	${FILES.o}
+	${AR} ${ARFLAGS} ${LIBNAME} ${FILES.o}
+
+install: ${LIBNAME} ${FILES.h}
+	${CP} ${CPFLAGS} ${LIBNAME} ${LIBDIR}
+	${CP} ${CPFLAGS} ${FILES.h} ${HDRDIR}
+
+clean:
+	${RM_F} ${DEBRIS} ${FILES.o}
+
+realclean: clean
+	${RM_F} ${LIBNAME}
diff --git a/src/lib/posixver.h b/src/lib/posixver.h
new file mode 100644
index 00000000..4199cfed
--- /dev/null
+++ b/src/lib/posixver.h
@@ -0,0 +1,35 @@
+/*
+@(#)File:           posixver.h
+@(#)Purpose:        Request appropriate POSIX and X/Open Support
+@(#)Author:         J Leffler
+@(#)Copyright:      (C) JLSS 2010,2015-16
+@(#)Derivation:     posixver.h,v 1.3 2015/07/05 21:28:18 
+*/
+
+/*TABSTOP=4*/
+
+#ifndef JLSS_ID_POSIXVER_H
+#define JLSS_ID_POSIXVER_H
+
+/*
+** Include this file before including system headers.  By default, with
+** C99 support from the compiler, it requests POSIX 2001 support.  With
+** C89 support only, it requests POSIX 1997 support.  Override the
+** default behaviour by setting either _XOPEN_SOURCE or _POSIX_C_SOURCE.
+*/
+
+/* _XOPEN_SOURCE 700 is loosely equivalent to _POSIX_C_SOURCE 200809L */
+/* _XOPEN_SOURCE 600 is loosely equivalent to _POSIX_C_SOURCE 200112L */
+/* _XOPEN_SOURCE 500 is loosely equivalent to _POSIX_C_SOURCE 199506L */
+
+#if !defined(_XOPEN_SOURCE) && !defined(_POSIX_C_SOURCE)
+#if defined(__cplusplus)
+#define _XOPEN_SOURCE 700   /* SUS v4, POSIX 1003.1 2008/13 (POSIX 2008/13) */
+#elif __STDC_VERSION__ >= 199901L
+#define _XOPEN_SOURCE 700   /* SUS v4, POSIX 1003.1 2008/13 (POSIX 2008/13) */
+#else
+#define _XOPEN_SOURCE 500   /* SUS v2, POSIX 1003.1 1997 */
+#endif /* __STDC_VERSION__ */
+#endif /* !_XOPEN_SOURCE && !_POSIX_C_SOURCE */
+
+#endif /* JLSS_ID_POSIXVER_H */
diff --git a/src/lib/stderr.c b/src/lib/stderr.c
new file mode 100644
index 00000000..51b4976e
--- /dev/null
+++ b/src/lib/stderr.c
@@ -0,0 +1,500 @@
+/*
+@(#)File:           stderr.c
+@(#)Purpose:        Error reporting routines
+@(#)Author:         J Leffler
+@(#)Copyright:      (C) JLSS 1988-91,1996-99,2001,2003,2005-11,2013,2015-16
+@(#)Derivation:     stderr.c,v 10.14 2015/06/02 03:04:32
+*/
+
+/*TABSTOP=4*/
+
+#include "posixver.h"
+#include "stderr.h"     /* Includes config.h if available */
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <time.h>
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#else
+extern int getpid(void);
+#endif /* HAVE_UNISTD_H */
+
+enum { MAX_MSGLEN = 2048 };
+
+/* Find sub-second timing mechanism */
+#if defined(HAVE_CLOCK_GETTIME)
+/* Uses <time.h> */
+#elif defined(HAVE_GETTIMEOFDAY)
+/* Mac OS X 10.10.3 does not have clock_gettime() yet */
+#include <sys/time.h>
+#else
+/* No sub-second timing */
+#endif
+
+static const char def_format[] = "%Y-%m-%d %H:%M:%S";
+static const char *tm_format = def_format;
+static char arg0[ERR_MAXLEN_ARGV0+1] = "**undefined**";
+
+/* Permitted default error flags */
+enum { ERR_LOGTIME = ERR_STAMP | ERR_MILLI | ERR_MICRO | ERR_NANO };
+enum { ERR_LOGOPTS = ERR_NOFLUSH | ERR_EXIT | ERR_ABORT | ERR_LOGTIME |
+                     ERR_NOARG0  | ERR_PID  | ERR_ERRNO };
+static int   err_flags = 0;     /* Default error flags (ERR_STAMP, ERR_PID, etc) */
+
+/* File where messages go */
+static FILE *errout =  0;
+
+/*
+** err_???_print() functions are named systematically, and are all static.
+**
+** err_[ev][crx][fn]_print():
+** --   e   takes ellipsis argument
+** --   v   takes va_list argument
+** --   c   conditionally exits
+** --   r   returns (no exit)
+** --   x   exits (no return)
+** --   f   takes file pointer
+** --   n   no file pointer (use errout)
+**
+** NB: no-return and printf-like can only be attached to declarations, not definitions.
+*/
+
+static NORETURN void err_vxf_print(FILE *fp, int flags, int estat, const char *format, va_list args);
+static NORETURN void err_vxn_print(int flags, int estat, const char *format, va_list args);
+static NORETURN void err_exn_print(int flags, int estat, const char *format, ...)
+                PRINTFLIKE(3,4);
+static NORETURN void err_terminate(int flags, int estat);
+
+/*
+** Set default log options, returning old value.
+** Setting ERR_EXIT and ERR_ABORT is permitted but not recommended.
+*/
+int err_setlogopts(int new_opts)
+{
+    int old_opts = err_flags;
+    err_flags = new_opts & ERR_LOGOPTS;
+    return(old_opts);
+}
+
+/* Return default log options */
+int err_getlogopts(void)
+{
+    return(err_flags);
+}
+
+/* Change the definition of 'stderr', reporting on the old one too */
+/* NB: using err_stderr((FILE *)0) simply reports the current 'stderr' */
+FILE *(err_stderr)(FILE *newerr)
+{
+    FILE *old;
+
+    if (errout == 0)
+        errout = stderr;
+    old = errout;
+    if (newerr != 0)
+        errout = newerr;
+    return(old);
+}
+
+/* Return stored basename of command */
+const char *(err_getarg0)(void)
+{
+    return(arg0);
+}
+
+/* Store basename of command, excluding trailing slashes */
+void (err_setarg0)(const char *argv0)
+{
+    /* Ignore three pathological program names -- NULL, "/" and "" */
+    if (argv0 != 0 && *argv0 != '\0' && (*argv0 != '/' || *(argv0 + 1) != '\0'))
+    {
+        const char *cp;
+        size_t nbytes = sizeof(arg0) - 1;
+
+        if ((cp = strrchr(argv0, '/')) == 0)
+        {
+            /* Basename of file only */
+            cp = argv0;
+        }
+        else if (*(cp + 1) != '\0')
+        {
+            /* Regular pathname containing slashes but not trailing slashes */
+            cp++;
+        }
+        else
+        {
+            /* Skip backwards over trailing slashes */
+            const char *ep = cp;
+            while (ep > argv0 && *ep == '/')
+                ep--;
+            /* Skip backwards over non-slashes */
+            cp = ep;
+            while (cp > argv0 && *cp != '/')
+                cp--;
+            assert(ep >= cp);
+            cp++;
+            nbytes = (size_t)(ep - cp) + 1;
+            if (nbytes > sizeof(arg0) - 1)
+                nbytes = sizeof(arg0) - 1;
+        }
+        strncpy(arg0, cp, nbytes);
+        arg0[nbytes] = '\0';
+    }
+}
+
+const char *(err_rcs_string)(const char *s2, char *buffer, size_t buflen)
+{
+    const char *src = s2;
+    char *dst = buffer;
+    char *end = buffer + buflen - 1;
+
+    /*
+    ** Bother RCS!  We've probably been given something like:
+    ** "$Revision: 10.14 $ ($Date: 2015/06/02 03:04:32 $)"
+    ** We only want to emit "7.5 (2001/08/11 06:25:48)".
+    ** Skip the components between '$' and ': ', copy up to ' $',
+    ** repeating as necessary.  And we have to test for overflow!
+    ** Also work with the unexpanded forms of keywords ($Keyword$).
+    ** Never needed this with SCCS!
+    */
+    while (*src != '\0' && dst < end)
+    {
+        while (*src != '\0' && *src != '$')
+        {
+            *dst++ = *src++;
+            if (dst >= end)
+                break;
+        }
+        if (*src == '$')
+            src++;
+        while (*src != '\0' && *src != ':' && *src != '$')
+            src++;
+        if (*src == '\0')
+            break;
+        if (*src == '$')
+        {
+            /* Unexpanded keyword '$Keyword$' notation */
+            src++;
+            continue;
+        }
+        if (*src == ':')
+            src++;
+        if (*src == ' ')
+            src++;
+        while (*src != '\0' && *src != '$')
+        {
+            /* Map / in 2009/02/15 to dash */
+            /* Heuristic - maps slashes surrounded by digits to dashes */
+            char c = *src++;
+            if (c == '/' && isdigit(*src) && isdigit(*(src-2)))
+                c = '-';
+            *dst++ = c;
+            if (dst >= end)
+                break;
+        }
+        if (*src == '$')
+        {
+            if (*(dst-1) == ' ')
+                dst--;
+            src++;
+        }
+    }
+    *dst = '\0';
+    return(buffer);
+}
+
+/* Similar to, but different from, Time in timer.h */
+typedef struct Time
+{
+    time_t tv_sec;
+    long   tv_nsec;
+} Time;
+
+static Time now(void)
+{
+    Time clk;
+#if defined(HAVE_CLOCK_GETTIME)
+    struct timespec ts;
+    clock_gettime(CLOCK_REALTIME, &ts);
+    clk.tv_sec = ts.tv_sec;
+    clk.tv_nsec = ts.tv_nsec;
+#elif defined(HAVE_GETTIMEOFDAY)
+    struct timeval tv;
+    gettimeofday(&tv, 0);
+    clk.tv_sec = tv.tv_sec;
+    clk.tv_nsec = 1000 * tv.tv_usec;
+#else
+    clk.tv_sec = time(0);
+    clk.tv_nsec = 0;
+#endif
+    return clk;
+}
+
+/* Format a time string for now (using ISO8601 format) */
+/* Allow for future settable time format with tm_format */
+static char *err_time(int flags, char *buffer, size_t buflen)
+{
+    Time clk = now();
+    struct tm *tp = localtime(&clk.tv_sec);
+    size_t nb = strftime(buffer, buflen, tm_format, tp);
+    if (flags & (ERR_NANO | ERR_MICRO | ERR_MILLI))
+    {
+        char subsec[12];
+        size_t ss_len;
+        if (flags & ERR_NANO)
+            ss_len = snprintf(subsec, sizeof(subsec), ".%.9ld", clk.tv_nsec);
+        else if (flags & ERR_MICRO)
+            ss_len = snprintf(subsec, sizeof(subsec), ".%.6ld", clk.tv_nsec / 1000);
+        else /* (flags & ERR_MILLI) */
+            ss_len = snprintf(subsec, sizeof(subsec), ".%.3ld", clk.tv_nsec / (1000 * 1000));
+        if (ss_len + nb + 1 < buflen)
+            strcpy(buffer + nb, subsec);
+    }
+    return(buffer);
+}
+
+/* err_stdio - report error via stdio */
+static void (err_stdio)(FILE *fp, int flags, int errnum, const char *format, va_list args)
+{
+    if ((flags & ERR_NOARG0) == 0)
+        fprintf(fp, "%s: ", arg0);
+    if (flags & ERR_LOGTIME)
+    {
+        char timbuf[48];
+        fprintf(fp, "%s - ", err_time(flags, timbuf, sizeof(timbuf)));
+    }
+    if (flags & ERR_PID)
+        fprintf(fp, "pid=%d: ", (int)getpid());
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+    vfprintf(fp, format, args);
+#pragma GCC diagnostic pop
+    if (flags & ERR_ERRNO)
+        fprintf(fp, "error (%d) %s\n", errnum, strerror(errnum));
+}
+
+/* Most fundamental (and flexible) error message printing routine - always returns */
+static void (err_vrf_print)(FILE *fp, int flags, const char *format, va_list args)
+{
+    int errnum = errno;     /* Capture errno before it is damaged! */
+
+    if ((flags & ERR_NOFLUSH) == 0)
+        fflush(0);
+
+    err_stdio(fp, flags, errnum, format, args);
+
+    fflush(fp);
+}
+
+/* Terminate program - abort or exit */
+static void err_terminate(int flags, int estat)
+{
+    assert(flags & (ERR_ABORT|ERR_EXIT));
+    if (flags & ERR_ABORT)
+        abort();
+    exit(estat);
+}
+
+/* Most fundamental (and flexible) error message printing routine - may return */
+static void (err_vcf_print)(FILE *fp, int flags, int estat, const char *format, va_list args)
+{
+    err_vrf_print(fp, flags, format, args);
+    if (flags & (ERR_ABORT|ERR_EXIT))
+        err_terminate(flags, estat);
+}
+
+/* Analog of err_vcf_print() which guarantees 'no return' */
+static void (err_vxf_print)(FILE *fp, int flags, int estat, const char *format, va_list args)
+{
+    err_vrf_print(fp, flags, format, args);
+    err_terminate(flags, estat);
+}
+
+/* External interface to err_vcf_print() - may return */
+void (err_logmsg)(FILE *fp, int flags, int estat, const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vcf_print(fp, flags, estat, format, args);
+    va_end(args);
+}
+
+/* Print error message to current error output - no return */
+static void (err_vxn_print)(int flags, int estat, const char *format, va_list args)
+{
+    if (errout == 0)
+        errout = stderr;
+    err_vxf_print(errout, flags, estat, format, args);
+}
+
+/* Print error message to current error output - no return */
+static void err_exn_print(int flags, int estat, const char *format, ...)
+{
+    va_list args;
+
+    va_start(args, format);
+    err_vxn_print(flags, estat, format, args);
+    va_end(args);
+}
+
+/* Print error message to nominated output - always returns */
+static void err_erf_print(FILE *fp, int flags, const char *format, ...)
+{
+    va_list args;
+
+    va_start(args, format);
+    err_vrf_print(fp, flags, format, args);
+    va_end(args);
+}
+
+/* Print message using current error file */
+void (err_print)(int flags, int estat, const char *format, va_list args)
+{
+    if (errout == 0)
+        errout = stderr;
+    err_vcf_print(errout, flags, estat, format, args);
+}
+
+static void err_vrn_print(int flags, const char *format, va_list args)
+{
+    if (errout == 0)
+        errout = stderr;
+    err_vrf_print(errout, flags, format, args);
+}
+
+/* Report warning including message from errno */
+void (err_sysrem)(const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vrn_print(ERR_SYSREM | err_getlogopts(), format, args);
+    va_end(args);
+}
+
+/* Report warning including message from errno */
+void (err_sysremark)(int errnum, const char *format, ...)
+{
+    va_list         args;
+    int old_errno = errno;
+
+    errno = errnum;
+    va_start(args, format);
+    err_vrn_print(ERR_SYSREM | err_getlogopts(), format, args);
+    va_end(args);
+    errno = old_errno;
+}
+
+/* Report error including message from errno */
+void (err_syserr)(const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vxn_print(ERR_SYSERR | err_getlogopts(), ERR_STAT, format, args);
+    va_end(args);
+}
+
+/* Report error including message from errno */
+void (err_syserror)(int errnum, const char *format, ...)
+{
+    va_list         args;
+    int old_errno = errno;
+
+    errno = errnum;
+    va_start(args, format);
+    err_vxn_print(ERR_SYSERR | err_getlogopts(), ERR_STAT, format, args);
+    va_end(args);
+    errno = old_errno;
+}
+
+/* Report warning */
+void (err_remark)(const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vrn_print(ERR_REM | err_getlogopts(), format, args);
+    va_end(args);
+}
+
+/* Report error */
+void (err_error)(const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vxn_print(ERR_ERR | err_getlogopts(), ERR_STAT, format, args);
+    va_end(args);
+}
+
+/* Report message - sometimes exiting too */
+void (err_report)(int flags, int estat, const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_print(flags, estat, format, args);
+    va_end(args);
+}
+
+/* Print usage message and exit with failure status */
+void (err_usage)(const char *s1)
+{
+    err_exn_print(ERR_NOARG0|ERR_EXIT, EXIT_FAILURE, "Usage: %s %s\n", err_getarg0(), s1);
+}
+
+/* Report failure and generate core dump */
+void (err_abort)(const char *format, ...)
+{
+    va_list         args;
+
+    va_start(args, format);
+    err_vxn_print(ERR_ABORT | err_getlogopts(), EXIT_FAILURE, format, args);
+    va_end(args);
+}
+
+/* Report version information (no exit), removing embedded RCS keyword strings (but not values) */
+void (err_printversion)(const char *program, const char *verinfo)
+{
+    char buffer[64];
+
+    if (strchr(verinfo, '$'))
+        verinfo = err_rcs_string(verinfo, buffer, sizeof(buffer));
+    err_erf_print(stdout, ERR_DEFAULT, "%s Version %s\n", program, verinfo);
+}
+
+/* Report version information and exit, removing embedded RCS keyword strings (but not values) */
+void (err_version)(const char *program, const char *verinfo)
+{
+    err_printversion(program, verinfo);
+    exit(EXIT_SUCCESS);
+}
+
+/* Report an internal error and exit */
+/* Abort if JLSS_INTERNAL_ERROR_ABORT set in environment */
+void (err_internal)(const char *function, const char *format, ...)
+{
+    va_list args;
+    int flags = ERR_EXIT;
+    const char *ev = getenv("JLSS_INTERNAL_ERROR_ABORT");
+
+    va_start(args, format);
+    if (ev != 0 && *ev != '\0')
+        flags = ERR_ABORT;  /* Generate core dump */
+    err_remark("unrecoverable internal error in function %s():\n", function);
+    err_vxn_print(flags | err_getlogopts(), EXIT_FAILURE, format, args);
+    va_end(args);
+}
+
+#ifdef TEST
+
+#error Use separate test program test.stderr.c
+
+#endif /* TEST */
diff --git a/src/lib/stderr.h b/src/lib/stderr.h
new file mode 100644
index 00000000..b53fde38
--- /dev/null
+++ b/src/lib/stderr.h
@@ -0,0 +1,96 @@
+/*
+@(#)File:           stderr.h
+@(#)Purpose:        Header file for standard error functions
+@(#)Author:         J Leffler
+@(#)Copyright:      (C) JLSS 1989-93,1996-99,2003,2005-11,2015-16
+@(#)Derivation:     stderr.h,v 10.10 2015/10/14 23:12:19
+*/
+
+#if !defined(STDERR_H)
+#define STDERR_H
+
+#if defined(HAVE_CONFIG_H)
+#include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+#include <stdio.h>
+#include <stdarg.h>
+
+/* Beware changing the NORETURN and PRINTFLIKE stanzas */
+#if !defined(NORETURN)
+#if __STDC_VERSION__ >= 201112L
+#define NORETURN      _Noreturn
+#elif defined(__GNUC__)
+#define NORETURN      __attribute__((noreturn))
+#else
+#define NORETURN      /* If only */
+#endif /* __STDC_VERSION__ || __GNUC__ */
+#endif /* NORETURN */
+
+#if !defined(PRINTFLIKE)
+#if defined(__GNUC__)
+#define PRINTFLIKE(n,m) __attribute__((format(printf,n,m)))
+#else
+#define PRINTFLIKE(n,m) /* If only */
+#endif /* __GNUC__ */
+#endif /* PRINTFLIKE */
+
+/* -- Definitions for error handling */
+
+enum { ERR_STAT    = 1 };           /* Default exit status     */
+
+enum { ERR_DEFAULT = 0x0000 };      /* Default flag                      */
+enum { ERR_NOFLUSH = 0x0001 };      /* Do not flush open files           */
+enum { ERR_EXIT    = 0x0004 };      /* Exit  -- do not return            */
+enum { ERR_ABORT   = 0x0008 };      /* Abort -- do not return            */
+enum { ERR_STAMP   = 0x0020 };      /* Timestamp messages (whole second) */
+enum { ERR_NOARG0  = 0x0040 };      /* Do not print arg0 prefix          */
+enum { ERR_PID     = 0x0080 };      /* Include pid=nnnnn info            */
+enum { ERR_ERRNO   = 0x0100 };      /* Include system error              */
+enum { ERR_MILLI   = 0x0200 };      /* Timestamp messages (millisecond)  */
+enum { ERR_MICRO   = 0x0400 };      /* Timestamp messages (microsecond)  */
+enum { ERR_NANO    = 0x0800 };      /* Timestamp messages (nanosecond)   */
+
+/* -- Standard combinations of flags */
+
+enum { ERR_REM    = ERR_DEFAULT       };
+enum { ERR_ERR    = ERR_EXIT          };
+enum { ERR_ABT    = ERR_ABORT         };
+enum { ERR_LOG    = ERR_STAMP|ERR_PID };
+enum { ERR_SYSREM = ERR_REM|ERR_ERRNO };
+enum { ERR_SYSERR = ERR_ERR|ERR_ERRNO };
+
+/* -- Maximum recorded length of argv[0]; extra is truncated */
+
+enum { ERR_MAXLEN_ARGV0 = 63 };
+
+/* -- Global definitions */
+
+extern const char *err_getarg0(void);
+extern void        err_setarg0(const char *argv0);
+
+extern FILE       *err_stderr(FILE *fp);
+extern const char *err_rcs_string(const char *s, char *buffer, size_t buflen);
+
+extern NORETURN void err_abort(const char *format, ...) PRINTFLIKE(1,2);
+extern NORETURN void err_error(const char *format, ...) PRINTFLIKE(1,2);
+extern NORETURN void err_help(const char *use_str, const char *hlp_str);
+extern NORETURN void err_helplist(const char *use_str, const char * const *help_list);
+extern NORETURN void err_internal(const char *function, const char *format, ...) PRINTFLIKE(2,3);
+extern NORETURN void err_syserr(const char *format, ...) PRINTFLIKE(1,2);
+extern NORETURN void err_syserror(int errnum, const char *format, ...) PRINTFLIKE(2,3);
+extern NORETURN void err_usage(const char *usestr);
+extern NORETURN void err_version(const char *program, const char *verinfo);
+
+extern void err_logmsg(FILE *fp, int flags, int estat, const char *format, ...) PRINTFLIKE(4,5);
+extern void err_print(int flags, int estat, const char *format, va_list args);
+extern void err_printversion(const char *program, const char *verinfo);
+extern void err_remark(const char *format, ...) PRINTFLIKE(1,2);
+extern void err_report(int flags, int estat, const char *format, ...) PRINTFLIKE(3,4);
+extern void err_sysrem(const char *format, ...) PRINTFLIKE(1,2);
+extern void err_sysremark(int errnum, const char *format, ...) PRINTFLIKE(2,3);
+
+extern int  err_getlogopts(void);           /* Get default log options */
+extern int  err_setlogopts(int new_opts);   /* Set default log options */
+
+#endif /* STDERR_H */
diff --git a/src/makefile b/src/makefile
new file mode 100644
index 00000000..1a48571e
--- /dev/null
+++ b/src/makefile
@@ -0,0 +1,18 @@
+# Makefile for src directory in SOQ project
+
+include ../etc/soq.mk
+
+BUILD_DIRECTORIES = \
+	lib \
+	so-0429-4928 \
+	so-3333-8314 \
+	so-3388-7484 \
+	so-3757-7522 \
+	so-3775-3785 \
+	so-3799-7620 \
+	so-3807-9550 \
+
+.DEFAULT all:
+	+for dir in ${BUILD_DIRECTORIES}; \
+	do (echo "+++ $${dir}"; cd "$${dir}" && ${MAKE} $@ && echo "--- $${dir}") \
+	done
diff --git a/recv.c b/src/so-0429-4928/recv.c
similarity index 100%
rename from recv.c
rename to src/so-0429-4928/recv.c
diff --git a/send.c b/src/so-0429-4928/send.c
similarity index 100%
rename from send.c
rename to src/so-0429-4928/send.c
diff --git a/sets.c b/src/so-3109-6894/sets.c
similarity index 100%
rename from sets.c
rename to src/so-3109-6894/sets.c
diff --git a/sets.h b/src/so-3109-6894/sets.h
similarity index 100%
rename from sets.h
rename to src/so-3109-6894/sets.h
diff --git a/src/so-3333-8314/README.md b/src/so-3333-8314/README.md
new file mode 100644
index 00000000..f436e8f1
--- /dev/null
+++ b/src/so-3333-8314/README.md
@@ -0,0 +1,3 @@
+# Stack Overflow Question 3333-8314
+
+[SO 33338314](http://stackoverflow.com/q/33338314) triggered this code as partial solutions.
diff --git a/src/so-3333-8314/makefile b/src/so-3333-8314/makefile
new file mode 100644
index 00000000..3b030902
--- /dev/null
+++ b/src/so-3333-8314/makefile
@@ -0,0 +1,11 @@
+# SO 3333-8314
+
+include ../../etc/soq.mk
+
+PROG1  = ncm
+PROG2  = rotcols
+
+all:	${PROG1} ${PROG2}
+
+${PROG1}: ${LIBPATH}
+${PROG2}: ${LIBPATH}
diff --git a/src/so-3333-8314/ncm.c b/src/so-3333-8314/ncm.c
new file mode 100644
index 00000000..1b78a1c2
--- /dev/null
+++ b/src/so-3333-8314/ncm.c
@@ -0,0 +1,29 @@
+/* SO 33338314 - vignette (see rotcols.c for real code) */
+#include <stdio.h>
+#include "gcd.h"
+
+int main(void)
+{
+    for (int n = 4; n < 13; n++)
+    {
+        for (int m = 1; m < n; m++)
+        {
+            printf("n = %d, m = %d:\n", n, m);
+            int c = gcd(n, m);
+            for (int b = 0; b < c; b++)
+            {
+                int x = b;
+                int s = n / c;
+                printf("  Cycle %d: ", b+1);
+                for (int i = 0; i < s; i++)
+                {
+                    printf("%3d", x);
+                    x = (x + m) % n;
+                }
+                putchar('\n');
+            }
+        }
+        putchar('\n');
+    }
+    return 0;
+}
diff --git a/src/so-3333-8314/rotcols.c b/src/so-3333-8314/rotcols.c
new file mode 100644
index 00000000..6b8d3a97
--- /dev/null
+++ b/src/so-3333-8314/rotcols.c
@@ -0,0 +1,73 @@
+/* SO 33338314 */
+#include <stdio.h>
+#include "gcd.h"
+
+static void dump_matrix(int m, int n, int source[m][n])
+{
+    for (int i = 0; i < m; i++)
+    {
+        for (int j = 0; j < n; j++)
+            printf("%4d", source[i][j]);
+        putchar('\n');
+    }
+}
+
+static void init_matrix(int m, int n, int source[m][n])
+{
+    for (int i = 0; i < m; i++)
+    {
+        for (int j = 0; j < n; j++)
+            source[i][j] = (i + 1) * (j + 2);
+    }
+}
+
+static void rotate_1col(int n, int vector[n], int z)
+{
+    z %= n;
+    if (z != 0)
+    {
+        int c = gcd(n, z);
+        int s = n / c;
+        for (int r = 0; r < c; r++)
+        {
+            int x = r;
+            int t = vector[x];
+            for (int i = 0; i < s; i++)
+            {
+                int j = (x + z) % n;
+                int v = vector[j];
+                vector[j] = t;
+                x = j;
+                t = v;
+            }
+        }
+    }
+}
+
+static void rotate_cols(int m, int n, int source[m][n], int z)
+{
+    for (int i = 0; i < m; i++)
+        rotate_1col(n, source[i], z);
+}
+
+int main(void)
+{
+    int m = 3;
+
+    for (int n = 2; n < 9; n++)
+    {
+        int source[m][n];
+        for (int z = 0; z <= n; z++)
+        {
+            init_matrix(m, n, source);
+            printf("Initial:\n");
+            dump_matrix(m, n, source);
+            rotate_cols(m, n, source, z);
+            printf("Post-rotate %d:\n", z);
+            dump_matrix(m, n, source);
+            putchar('\n');
+        }
+    }
+
+    return 0;
+}
diff --git a/so.3775-3785.data b/src/so-3775-3785/so.3775-3785.data
similarity index 100%
rename from so.3775-3785.data
rename to src/so-3775-3785/so.3775-3785.data
diff --git a/so.3775-3785.py b/src/so-3775-3785/so.3775-3785.py
similarity index 100%
rename from so.3775-3785.py
rename to src/so-3775-3785/so.3775-3785.py