SAFE CRACK ---------- by Stephen Parry from ZX Computing, June/July 1984 Answer the questions and break into Stephen Parry's Southampton safe. This is not just another code-breaking game but a simple maths program for use in primary schools involving addition, subtraction and multiplication. There are fifteen boxes, each occupied by a red question mark (?) and every correct answer replaces the question mark with a blue pound sign (£). The object is of course to fill all the boxes with pound signs — if anything will attract and occupy the minds of children, it's money! Every wrong answer loses a pound sign but the computer will keep on asking questions until someone wins. Filling all the squares with pound signs will give a large fanfare of sound and a colourful screen display. The program runs by first calling the subroutine at 8900. This draws a colourful screen with accompanying sound and a sum is randomly devised in lines 7000 to 7050. To do this, line 7020 chooses whether addition, subtraction or multiplication is to be performed and line 7030 makes sure that if multiplication is chosen then the numbers are kept within the range of 1 to 12. Line 7040 chooses two numbers and the value 100 can easily be changed if smaller numbers are wanted. Line 7050 ensures that no negative numbers result from subtraction and then line 7060 builds the sum itself. After answering the question from a series of screen prompts. the child is immediately told the answer which is worked out in line 7120. Having compared the child’s answer with that of the computer, the program either jumps to a fail message which replaces the pound sign with a question mark or to line 7700, which places a pound sign in the next box. If the variable tot reaches 15, meaning that all the boxes have been filled, the subroutine at line 8000 is called which displays a win message and the usual "do you want another go" question is asked.