Type In – A DDP Verifier

In the late 70’s, early 80’s there were many magazines and books devoted to the personal computers of the time that contained programs that you could type into your computer, save and use. Though tedious it was often the only way many people could get new software for their orphaned systems. With this in mind I present DDP Verify, a small type in that will let you non-destructively verify if your tapes are good or not.

Let’s Make a Tape – Squashing a Bug

To begin with you will need a blank tape and a tape containing a copy of Smart Basic. The reason for two tapes is we will be creating a quick booting tape that will be used to verify other tapes. If you happen to run any of the programs with the Smart Basic tape in drive 1 IT WILL ERASE you Smart Basic tape. If you have an original Colecovision Smart Basic version 1.0 you will want to do something before you get started. You will want to squash a bug!

There is a bug in Smart Basic in that every time you load a program with a REM or DATA statement it will add an extra space after the REM or DATA, eventually pushing your code off the line and ruining the code. To fix this is easy:

  1. Start Smart Basic
  2. Type the following code:10 PRINT “Data bump bug fix”
    20 POKE 15830,8
    30 POKE 15831,55
    40 POKE 15832,19
    50 POKE 15824,216
    60 NEW
  3. Save the code as HELLO on the tape using save HELLO (it is case sensitive)
  4. Reboot your tape and it should tell you the data bug is fixed, if not then you saved it with the wrong name

If you already have a HELLO program on your tape, load it and add the code above to it in the beginning. You can eliminate line 10 and line 60 if you want and combine all the POKEs onto one line.

Typing in the Program

Now we are ready to start typing in earnest! To create the DDP Verify tape we need to type in the loader which reads the data and the data statements which holds the program. First I will explain the loader:


1 HIMEM :39000: R = 40004: B = 40128
2 DATA 1,0,0,17,0,0,62,8,33,192,156,205,246,252,201
3 FOR K = 40000 TO 40014: READ D: POKE K,D: NEXT K
6 IF A = -3 THEN CALL 40000: PRINT " DONE":END
8 IF A = -1 THEN READ A: FOR K = 0 TO 15: POKE B,A: B = B + 1: NEXT K: GOTO 5
9 POKE B,A: B = B + 1: GOTO 5

How it works:

1 > Tell SB to not touch memory above 39000 and set up the variables R and B. R holds where we will poke tape records and B is where our tape record buffer is.

2 > This is a small machine language (ML) code that we use to access the EOS routines to write a block to tape. The variable R which we defined in line 1 points to the block low byte. Here is the code:

LD BC,0 ;Block High Byte
LD DE,0 ;Block Low Byte
LD A,8 ;Tape drive 1
LD HL,40128 ;Buffer
CALL 0FCF6h ;Write one block

3 > This line reads in the ML in line 2 and pokes it into memory starting at address 40128 which we defined on line 1

4 > This line pauses and prompts you to put in the blank tape we will be turning into a the Verify tape – PLEASE follow this instruction.

5 > This reads in a byte from the data statements. The byte can have one of 4 values:

0 – 255 = This is a byte that will be poked into memory
-1 = This tells the loader that the next byte to be read gets poked into memory 16 times – This saves on typing
-2 = This tells the loader that the next byte contains the record number this block of data gets saved to
-3 = This tells the loader we are done, write the block to tape and end

6 – 8 > These lines process the data that is read as described above

9 > Pokes the data into memory at B, increments B and then loops back to line 5 to do more

Once you have typed in the LOADER program save it. Now we will type in the code:

DDP Verify

30 DATA -2,0
31 DATA 243,049,142,211,120,050,255,255,033,050,201,017,088,246,001,003
32 DATA 000,237,176,001,000,000,205,032,253,001,192,001,205,032,253,033
33 DATA 000,000,062,003,205,041,253,033,000,008,062,002,205,041,253,205
34 DATA 056,253,017,000,004,033,000,000,001,128,000,205,023,253,033,192
35 DATA 011,062,004,205,041,253,033,000,056,062,001,205,041,253,033,128
36 DATA 056,175,205,041,253,001,001,007,205,032,253,014,003,006,001,022
37 DATA 000,030,000,033,192,011,025,017,032,000,121,203,007,203,007,203
38 DATA 007,203,007,128,205,038,253,006,031,014,023,022,000,030,000,033
39 DATA 000,008,205,054,252,062,032,017,000,003,033,000,008,205,038,253
40 DATA 062,000,050,053,201,033,054,201,205,041,201,033,187,201,205,013
41 DATA 201,205,108,252,033,005,202,205,013,201,062,028,022,000,030,006
42 DATA 205,057,252,006,255,014,001,017,000,000,197,033,184,201,205,041
43 DATA 201,001,000,000,058,255,255,033,000,001,205,243,252,032,004,062
44 DATA 079,024,020,033,110,202,205,013,201,205,108,252,033,005,202,205
45 DATA 013,201,062,127,050,053,201,205,051,252,193,019,016,204,062,001
46 DATA 185,032,006,014,000,006,001,024,193,033,007,202,058,053,201,183
47 DATA 040,003,033,059,202,205,013,201,205,108,252,024,131,058,166,254
48 DATA 087,058,165,254,095,213,062,028,022,000,030,020,205,057,252,205
49 DATA 041,201,209,062,028,205,057,252,201,126,183,200,205,057,252,035
50 DATA 024,247,000,000,000,000,012,043,045,045,045,045,045,045,045,045
51 DATA 045,045,045,045,045,045,045,045,045,045,045,045,045,045,045,045
52 DATA 045,045,045,045,045,045,043,124,032,068,068,080,032,086,101,114
53 DATA 105,102,121,032,040,099,041,032,087,105,108,108,105,097,109,032
54 DATA 072,105,099,107,115,032,124,043,045,045,045,045,045,045,045,045
55 DATA 045,045,045,045,045,045,045,045,045,045,045,045,045,045,045,045
56 DATA 045,045,045,045,045,045,043,013,010,032,111,032,061,032,082,101
57 DATA 097,100,105,110,103,032,079,032,061,032,080,097,115,115,032,127
58 DATA 032,061,032,070,097,105,108,000,111,008,000,032,082,101,112,108
59 DATA 097,099,101,032,116,097,112,101,032,119,105,116,104,032,116,104
60 DATA 101,032,116,097,112,101,013,010,032,116,111,032,098,101,032,118
61 DATA 101,114,105,102,105,101,100,032,097,110,100,032,116,104,101,110
62 DATA 013,010,032,112,114,101,115,115,032,097,110,121,032,107,101,121
63 DATA 046,046,046,032,000,024,000,032,078,111,032,101,114,114,111,114
64 DATA 115,032,112,114,101,115,101,110,116,044,032,112,114,101,115,115
65 DATA 032,097,110,121,013,010,032,107,101,121,032,116,111,032,099,111
66 DATA 110,116,105,110,117,101,046,046,046,032,000,032,069,114,114,111
67 DATA 114,040,115,041,032,112,114,101,115,101,110,116,044,032,112,114
68 DATA 101,115,115,032,097,110,121,013,010,032,107,101,121,032,116,111
69 DATA 032,099,111,110,116,105,110,117,101,046,046,046,032,000,032,065
70 DATA 100,106,117,115,116,032,116,097,112,101,032,116,104,101,110,032
71 DATA 112,114,101,115,115,013,010,032,097,110,121,032,107,101,121,032
72 DATA 116,111,032,099,111,110,116,105,110,117,101,046,046,046,032,000
73 DATA -3

This is the code for DDP – Verify. Once you have typed in it save it as VERIFY. DO NOT RUN IT – If you do it will ruin the tape you have in the drive.

After saving VERIFY remove the SMART BASIC tape and put in the blank INITIALIZED one you made. Run VERIFY and follow the prompts. When done you should be able to reset the system and DDP Verify will start. You can then follow the prompts on the screen to start verifying your tapes.

The Screen

When DDP Verify is running it will show a ‘o’ as it is reading a bloc, and a ‘O’ if the black passes of the checkerboard if it doesn’t. If you want to know which block it is you can just count them on the screen. Each line is 32 blocks long so if you fail on the first column on row 3 then you failed on 2 * 32 + 1 or block 65. I kept things simple to decrease the amount of code and typing in.


If you decide to do this let me know.


  • Disk & Tape images to use in an emulator and the DDP Verify basic code VERIFY.ZIP

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