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Structure charts

What is a structure chart?

• A structure chart is a modelling tool used in the design stage of program development

• It helps to decompose a problem into smaller, manageable sub-tasks, representing each as a module

• Structure charts focus on what the program does, not how it does it

Example

• A program that asks a user to enter their username and password

• Checks if the password matches the stored password and uses a counter to track how many times it is checked

• If the password matches, a successful message is displayed, else after three failed attempts a ‘denied’ message is displayed

• A structure chart might look like:

Key features

Pseudocode from structure chart

• The first step is to create an identifier table

• Next, identify is any functions or procedures could be used

• Any finally, write the pseudocode

DECLARE Username : STRING
DECLARE Password : STRING
DECLARE StoredPass : STRING
DECLARE NoAttempts : INTEGER
DECLARE LoginSuccess : BOOLEAN StoredPass ← "admin123"
NoAttempts ← 0
LoginSuccess ← FALSE PROCEDURE GetCredentials() OUTPUT "Enter username: " INPUT Username OUTPUT "Enter password: " INPUT Password
ENDPROCEDURE FUNCTION CheckPassword(P : STRING) RETURNS BOOLEAN IF P = StoredPass THEN RETURN TRUE ELSE RETURN FALSE ENDIF
ENDFUNCTION PROCEDURE ShowAccessMessage(Success : BOOLEAN) IF Success = TRUE THEN OUTPUT "Login successful" ELSE OUTPUT "Access denied" ENDIF
ENDPROCEDURE WHILE NoAttempts < 3 AND LoginSuccess = FALSE CALL GetCredentials() LoginSuccess ← CheckPassword(Password) IF LoginSuccess = FALSE THEN OUTPUT "Incorrect password" NoAttempts ← NoAttempts + 1 ENDIF
ENDWHILE CALL ShowAccessMessage(LoginSuccess)