5_if_else.pdf

PRG 155 – Programming Fundamentals Using C 5. Decision Control Statements in C  if statement  if-else and else-if statements  switch-case statements if Statement  if statement is used to make a decision based on a condition.  Condition can be an expression (examples: if(x + y...

PRG 155 – Programming Fundamentals Using C 5. Decision Control Statements in C  if statement  if-else and else-if statements  switch-case statements if Statement  if statement is used to make a decision based on a condition.  Condition can be an expression (examples: if(x + y) or if(num1>5)) of a direct value (example: if(5))  If the expression produces zero, or direct value is zero, the condition becomes FALSE. For all other values, the condition is TRUE. Examples: if(10) is TRUE if(0) is FALSE if(x + y) is TRUE if (x+y) is not equal to zero if(num1 > 5) is TRUE if the value of variable num is greater than 5 1 PRG 155 – Programming Fundamentals Using C Simple if statement  The if statement evaluates the condition. If it is TRUE, it executes the block of code that follows. If the condition is FALSE, it will skip this code.  Used when there is only one option that is executed or not based on a condition. Syntax if Statement Flowchart Example: if (number < 0) //checks if number is a negative number { printf(“You entered negative number: %d”, number); } 2 PRG 155 – Programming Fundamentals Using C if - else statement The if-else evaluates the condition. If it is TRUE, it executes the block of code that follows. If the condition is FALSE, it executes the second block of code. Syntax if-else Statement Flowchart Example: if (number < 0) //checks if a number is a negative number { printf(“You entered negative number: %d”, number); } else { printf(“You entered zero or positive number: %d”, number); } 3 PRG 155 – Programming Fundamentals Using C Nested if statement The if-else statement is inside another if-else statement Syntax if (condition1) { if (condition2) { //statements to be executed if condition1 & condition2 are TRUE } else { } } else { //statements to be executed if condition1 is false } Example: if (number < 0) //checks if number is a negative number { printf(“You entered negative number: %d”, number); } else { if (number == 0) //checks if number is equal to zero { printf(“You entered zero”); } else { printf(“You entered positive number: %d”, number); } } 4 PRG 155 – Programming Fundamentals Using C if – else – if statement (if-else ladder) The if-else ladder allows for multiple test expressions to be checked and to execute different codes for more than two conditions. Syntax if (condition1) { //statements to be executed if condition1 is TRUE } else if (condition2) { //statements to be executed if condition1 is FALSE and condition2 is TRUE } else if (condition3) { //statements to be executed if condition1&condition2 are FALSE, // and condition3 is TRUE }... else { //statement to be executed if all conditions are FALSE } Example: if(number < 0) //checks if number is a negative number { printf(“You entered negative number: %d”, number); } else if (number > 0) //checks if number is a positive number { printf(“You entered positive number: %d”, number); } else { printf(“You entered zero”); } 5 PRG 155 – Programming Fundamentals Using C References  Tan, H.H., and T.B. D’Orazio. C Programming for Engineering & Computer Science. USA: WCB McGRaw-Hill. 1999. Print.  C if, if...else and Nested if...else Statement. N.p., n.d. Web. 09 Feb. 2017.. 6