Syntactic Sum

The ‘SYNTACTIC SUM’ shown after the programs is a convenient parity check which was required by the editors of the now defunct Sinclair oriented newsletter SYNTAX ZX80, a publication of the Harvard Group. It is apparently a code sum of all characters in the program listing. Matching this number insures that it has been ‘punched in’ correctly (two canceling errors which defeat the check sum is most unlikely). This sum was obtained by running a 24 byte MC program (AF 47 67 6F E5 2A 0C 40 11 7D 40 2B 4E E3 09 E3 E5 ED 52 E1 20 F5 C1 C9 in hex) which was poked in above a lowered RAM TOP before loading or typing in the program to be tested. For example, with 16K RAM, lower RAM TOP to 32743 (POKE 16389,127 & POKE 16388,231), place MC bytes from 32744 to 32767 and get check sum with command PRINT USR 32744. Use the hex loader of your choice or, for so short a program manual conversion to decimal code and 24 POKEs isn’t prohibitive. Incidently, the sum for CALPR-1 requires use of inverted characters for EXP in line 37 and the token AND in line 80. (Syntactic Sum program reprinted by permission of the Harvard Group.-ed.)

 1 REM SYNTACTIC SUM LOADER
 2 REM 16K VERSION
 3 REM PART ONE
10 POKE 16389,127
15 POKE 16388,231
20 NEW

 1 REM SYNTACTIC SUM LOADER
 2 REM 16K VERSION
 3 REM PART TWO
10 FOR I=1 TO 24
15 SCROLL
20 PRINT "INPUT NO. ";I,
25 INPUT A$
30 PRINT A$
35 POKE I+32743,(16*CODE A$+CODE A$(2)-476)
40 NEXT I

INPUT NO. 1   AF   INPUT NO. 13  4E
INPUT NO. 2   47   INPUT NO. 14  E3
INPUT NO. 3   67   INPUT NO. 15  09
INPUT NO. 4   6F   INPUT NO. 16  E3
INPUT NO. 5   E5   INPUT NO. 17  E5
INPUT NO. 6   2A   INPUT NO. 18  ED
INPUT NO. 7   0C   INPUT NO. 19  52
INPUT NO. 8   40   INPUT NO. 20  E1
INPUT NO. 9   11   INPUT NO. 21  20
INPUT NO. 10  7D   INPUT NO. 22  F5
INPUT NO. 11  40   INPUT NO. 23  C1
INPUT NO. 12  2B   INPUT NO. 24  C9