[TUHS] origin of string.h and ctype.h

Jon Steinhart &lt;jon(a)fourwinds.com&gt; asked this question (not on tuhs). It highlights some less well known contributors to research Unix. The -1,0,1 return from comparisons stems from the interface of qsort, which was written by Lee McMahon. As far as I know, the interface for the comparison-function parameter originated with him, but conceivably he borrowed it from some other sort utility. The negative-zero-positive convention for the return value encouraged (and perhaps was motivated by) this trivial comparison function for integers int compar(a,b) { return(a-b); } This screws up on overflow, so cautious folks would write it with comparisons. And -1,0,1 were the easiest conventional values to return: int compar(a,b) { if(a<b) return(-1); if(a>b) return(1); return(0); } qsort was in v2. In v3 a string-comparison routine called "compar" appeared, with a man page titled "string comparison for sort". So the convention was established early on. Compar provided the model for strcmp, one of a package of basic string operations that came much later, in v7, under the banner of string.h and ctype.h. These packages were introduced at the urging of Nils-Peter Nelson, a good friend of the Unix lab, who was in the Bell Labs comp center. Here's the story in his own words. I wrote a memo to dmr with some suggestions for additions to C. I asked for the str... because the mainframes had single instructions to implement them. I know for sure I had a blindingly fast implementation of isupper, ispunct, etc. I had a table of length 128 integers for the ascii character set; I assigned bits for upper, lower, numeric, punct, control, etc. So ispunct(c) became #define PUNCT 0400 return(qtable[c]&PUNCT) instead of if(c==':' || c ==';' || ... [or switch(c) { default: return 0; case ':': case ';': ... return 1; } MDM] dmr argued people could easily write their own but when I showed him my qtable was 20 times faster he gave in. I also asked for type logical which dmr implemented as unsigned, which was especially useful when bitfields were implemented (a 2 bit int would have values -2, -1, 0, 1 instead of 0, 1, 2, 3). I requested a way to interject assembler, which became asm() (yes, a bad idea).