A simple banking program needs to perform the following operations on an account balance: Deposit money Withdraw money (checking sufficient funds) Check bal...

(a) Four separate subprograms for a banking system:

PROCEDURE Deposit(BYREF Balance : REAL, Amount : REAL)
    IF Amount > 0 THEN
        Balance ← Balance + Amount
        OUTPUT "Deposited: ", Amount, ". New balance: ", Balance
    ELSE
        OUTPUT "Invalid amount"
    ENDIF
ENDPROCEDURE

Deposit uses a procedure with BYREF to modify the balance directly. It validates that the amount is positive. [1]

FUNCTION Withdraw(BYREF Balance : REAL, Amount : REAL) RETURNS BOOLEAN
    IF Amount <= 0 THEN
        OUTPUT "Invalid amount"
        RETURN FALSE
    ENDIF
    IF Amount > Balance THEN
        OUTPUT "Insufficient funds. Balance: ", Balance
        RETURN FALSE
    ENDIF
    Balance ← Balance - Amount
    OUTPUT "Withdrawn: ", Amount, ". New balance: ", Balance
    RETURN TRUE
ENDFUNCTION

Withdraw checks both validity and sufficient funds before deducting. It returns a Boolean indicating success. [1]

PROCEDURE CheckBalance(Balance : REAL)
    OUTPUT "Current balance: ", Balance
ENDPROCEDURE

CheckBalance passes Balance by value (read-only) since it only displays the value. [1]

FUNCTION CalculateInterest(Balance : REAL) RETURNS REAL
    RETURN Balance * 0.02
ENDFUNCTION

CalculateInterest is a function because it computes and returns a value (2% of the balance) without modifying the balance itself. [1]