Procedures with Parameters

• steps in problem solution
• general operations

This has several limitations:

• only able to manipulate:
  • locally declared variables and constants
  • specific global variables and constants
• same data manipulated on every call

Parameters

A parameter = argument to a procedure

• procedure = operation
• parameter = operand

The procedure declaration shows the number and type of arguments

• formal parameters

The procedure call supplies specific arguments

• actual parameters

Parameter modes indicate how data may be communicated between the calling and called procedure.

Parameter association mechanisms define which actual parameters in the caller are associated with which formal parameters in the called procedure.

Parameters with bottom-up programming

procedure = operation, parameter = operand

    PUT (23);
    PUT (N, WIDTH=>2);
    PUT ("Simon says, wake up!");
    F(x)
    GET (height);
    get_integer (num, 1, 10);
    get_integer (mark, 0, 100);

parameters allow manipulation of different data

Parameters with top-down decomposition

procedure = sub-task, parameter = data/result

    begin
        get_data (data);
        compute_answer (data, answer);
        display(answer);
    end;

parameters allow communication between procedures