Basic Logic – Chapter 3

1. Basic Logic – Chapter 3 IPC144 Week 3

2. Sequential Logic • Statements executed sequentially – one after another • Limited usefulness • All programs shown so far have been sequential • Often need to perform logic based on conditions  conditional logic

3. Conditional example : movie tickets • Movie tickets are to be sold using the following prices: Adult: $10 Child under 6 years: $4 Student(6-19 years): $7 Senior citizen(65 yrs and over): $7 • Express this using conditional logic!

4. Conditional Logic • Condition tested and one action or another will be performed • A condition in C can include variables, literal values (eg 3, "a", "$", …), relational operators (> < == >= <= !=), arithmetic operators (= - * / …), … • Example of condition: age > 19 • One method of implementing conditional logic in C: if statement • Simple if statement syntax if (condition) statement;

5. Simple Conditional Logic Example • Calculate the cost of doughnuts bought at $0.60 per doughnut • GST of 7% is charged if fewer than 6 doughnuts bought • Display the amount of GST charged and the total amount owed • Write a C program to do this!

6. If Statement Example Write C program for this problem!

7. Code blocks • Groups of C statements can be treated as one logical statement by enclosing within brace {} brackets • Group of statements within main are treated as a big block of code • Can use additional {} within main to group statements, eg within an if statement

8. Code blocks example • Assume PST of 8% is also to be charged if fewer than 6 doughnuts bought … if (qty < 6) { GSTamt = subtotal * 0.07; PSTamt = subtotal * 0.08; } total = subtotal + GSTamt + PSTamt; …

9. main() { int qty; double subtotal, total, PSTamt, GSTamt =0; printf("Enter number of dougnuts: ") scanf("%d", &qty); subtotal = qty * 0.60; if (qty < 6) { GSTamt = subtotal * 0.07; PSTamt = subtotal * 0.08; } total = subtotal + GSTamt + PSTamt; printf("Total owed: $%.2lf , GST:$%.2lf, PST:$.2lf\n", total, GSTamt, PSTamt); }