Programming

You will be able to

• Describe count-controlled (FOR), pre-condition (WHILE) and post-condition (REPEAT … UNTIL) loops.
• Explain why a WHILE loop may run its body zero times but a REPEAT loop always runs it at least once.
• Select a suitable loop for a task: FOR for a known number of repeats, REPEAT or WHILE to repeat until a condition is met.

You will be able to

• Use LENGTH, SUBSTRING, UCASE and LCASE to handle strings, stating the position of the first character.
• Calculate the results of the library routines DIV, MOD and ROUND, and use MOD to test for exact division.
• Describe what RANDOM() returns and how to turn it into a random whole number in a range.

You will be able to

• Describe the difference between a procedure (called with CALL) and a function (returns a value used in an expression).
• Explain how a parameter passes a value into a routine when it is called.
• Explain the scope of local and global variables, including a local variable with the same name as a global one.

You will be able to

• Declare and use one- and two-dimensional arrays, reading and writing an element by its index.
• Explain why an index outside the declared lower and upper bounds is an error.
• Describe how nested FOR loops visit every element of a 2D array, row by row, and total each row.

You will be able to

• Explain why programs store data in files: the data is kept permanently, after the program ends.
• Use OPENFILE, READFILE, WRITEFILE and CLOSEFILE, stating that FOR WRITE overwrites a file and each READFILE reads the next line.
• State why a file should always be closed after use.