Named GOSUB's

M.R. Smith

In a previous article, (COMPUTE! #12), I showed how to use the Ampersand instruction in Applesoft to permit instructions of the form:

10 FIRST = 1000
20 DEUX = 2000
30 THIRD = 3000
40 & GOSUB FIRST
50 & GOTO THIRD

In Applesoft BASIC, named GOSUB's and GOTO's are not normally allowed.

The machine language program given in that article did not allow the use of names in ON... GOSUB or ON...GOTO statements. The following machine language program rectifies that problem.

The following statements are now permitted:

60 FOURTH = 4000
70 NUM = INT(1 + RND(2))
80 & ON NUM GOSUB FIRST, DEUX
90 & ON NUM GOTO THIRD, FOURTH

Using statements of this form makes it much easier to follow programs containing a large number of subroutines. In addition, it is much easier to remember the name of a subroutine rather than its number.

I am presently working on an extension to these statements to allow the passing of variables to a subroutine. That means statements of the form:

& GOSUB CALCULATE(A, B, C)

allowing the power of FORTRAN subroutine calls.

Description Of The BASIC Program

Line 20. Load the machine language program.

Line 20–100. Demonstrates the & GOSUB and & GOTO statements.

Line 110–180. Demonstrates the & ON... GOSUB and & ON...GOTO statements.

Lines 1000–3500. Demonstration subroutines and statements.

Lines 5000–6160. This subroutine loads and checks the machine language program. Every 17th number is the simple sum of the previous 16 numbers. This allows the entry of the numbers to be checked. The machine language program can be saved using the instruction:

BSAVE NAMED.GO,A$300,L$88

and called into your programs using the instruction:

10 PRINT CHR$(4);"BRUN NAMED.GO"

before any call to the ampersand (&) statements are made.

Program 1.

300. 387
0300- A9 4C 8D F5 03 A9 10 8D
0308- F6 03 A9 03 8D F7 03 60
0310- C9 B0 F0 0D C9 AB F0 29
0318- C9 B4 F0 31 A2 10 4C 12
0320- D4 20 B1 00 A9 03 20 D6
0328- D3 A5 B9 48 A5 B8 48 A5
0330- 76 48 A5 75 48 A9 B0 48
0338- 20 B7 00 20 44 03 4C D2
0340- D7 20 B1 00 20 7B DD 20
0348- 52 E7 4C 41 D9 20 B1 00
0350- 20 F8 E6 48 C9 B0 F0 0D
0358- C9 AB F0 09 C9 AF D0 BC
0360- 68 20 B1 00 48 C6 A1 D0
0368- 04 68 4C 10 03 A5 A1 48
0370- 20 B1 00 20 7B DD 20 52
0378- E7 20 B7 00 C9 2C DO 05
0380- 68 85 A1 DO E0 68 68 60
*

Program 2.

1 REM M. R. SMITH
2 REM MAY 1981
3 REM
10 REM LOAD THE ROUTINE  -  NORMA GOSUB
20 GOSUB 5000
30 REM ESTABLISH NAMES OF THE SUBROUTINES
40 FIRST = 1000 : DEUX = 1500 : THIRD = 2000
50 FOURTH = 2500 : FVTH = 3000 : SIXTH = 3500
60 REM  DEMONSTRATE NAMED GOSUB'S
70 & GOSUB FIRST
80 &  GOSUB DEUX
90 REM DEMONSTRATE NAMED GOTO
100 &  GOTO FOURTH
110 REM DEMONSTRATE NAMED ON...GOSUB
120 NUM =  INT (1 + 3 *  RND (1))
130 & ON NUM GOSUB FIRST, DEUX, THIRD
140 REM DEMONSTRATE NAMED ON...GOTO
150 FOR J = 1 TO 1000 : NEXT : REM DELAY
160 NUM =  INT (1 + 3 * RND (1))
170 &  ON NUM GOTO FOURTH, FVTH, SIXTH
180 STOP
190 REM
970 REM DUMMY SUBROUTINES AND LINES
980 REM
990 REM FIRST SUBROUTINE
1000 PRINT : PRINT "IN SUBROUTINE FIRST" : RETURN
1490 REM SECOND SUBROUTINE
1500 PRINT : PRINT "IN A DIFFERENT NAMED SUBROUTINE"
1510 PRINT "IN SUBROUTINE DEUX" : RETURN
1990 REM  THIRD SUBROUTINE
2000 PRINT : PRINT "IN SUBROUTINE THIRD" : RETURN
2490 REM LINE CALLED FOURTH
2500 PRINT : PRINT "LINE CALLED FOURTH": GOTO 120
2990 REM LINE CALLED FVTH
3000 PRINT : PRINT "LINE CALLED FVTH": GOTO 150
3490 REM LINE CALLED SIXTH
3500 PRINT : PRINT "LINE CALLED SIXTH": GOTO 150
4980 REM
4990 REM LOAD IN MACHINE LANGUAGE PROGRAM
5000 LOW = 768:HIGH = 903
5010 OK = 1
5020 REM LOAD IN GROUP OF SIXTEEN
5030 FOR J = LOW TO HIGH STEP 16
5040 CHECK = 0
5050 FOR K = J TO J + 15
5060 READ IT
5070 CHECK = CHECK + IT
5080 NEXT K
5090 REM CHECK IF CHECKSUM OKAY
5100 READ SUM
5110 L$ = "OKAY": IF CHECK < > SUM THEN L$ = "BAD":OK = 0
5120 PRINT L$
5130 NEXT J
5140 IF OK = 0 THEN STOP
5150 REM THINGS ARE OKAY - LOAD INTO MEMORY
5160 RESTORE : FOR J = LOW TO HIGH STEP 16
5170 FOR K = J TO J + 15: READ IT: POKE K,IT: NEXT K
5180 READ IT: NEXT J
5190 PRINT "BLOAD OKAY": PRINT : PRINT
5200 REM SET THE AMPERSAND VECTOR
5210 REM NOT NEEDED IF CALLED BY BRUN STATEMENT
5220 CALL 768: RETURN
6000 DATA 169,76,141,245,3,169,16,141,246
6010 DATA 3,169,3,141,247,3,96,1868
6020 DATA 201,176,240,13,201,171,240,41,201
6030 DATA 180,240,49,162,16,76,18,2225
6040 DATA 212,32,177,0,169,3,32,214,211
6050 DATA 165,185,72,165,184,72,165,2058
6060 DATA 118,72,165,117,72,169,176,72,32
6070 DATA 183,0,32,68,3,76,210,1565
6080 DATA 215,32,177,0,32,123,221,32,82
6090 DATA 231,76,65,217,32,177,0,1712
6100 DATA 32,248,230,72,201,176,240,13,201
6110 DATA 171,240,9,201,175,208,188,2605
6120 DATA 104,32,177,0,72,198,161,208,4
6130 DATA 104,76,16,3,165,161,72,1553
6140 DATA 32,177,0,32,123,221,32,82,231
6150 DATA 32,183,0,201,44,208,5,1603
6160 DATA 104,133,161,208,224,104,104,96,0,0,0,0,0,0,0,0,1134