Selection and Repetition Constructs

Abstract

Like other high-level programming languages, C has the ability to make decisions by comparing values. Two values can be tested for equality, for example, and one block of statements can be executed if the values are equal. Another block of statements, or no statements at all, can be executed if the values aren’t equal. The purpose of such decision-making statements should already be clear from the discussion of pseudocode commands in Chapter 1. Also, we have already used some implementations of the pseudocode IF…THEN…ELSE statement in Chapters 2 and 3 in code for reading files. For instance, in the statements

status=fscanf(infile,…); if (status == EOF) break;

and

infile=fopen(name,“r”);

if (infile == NULL)

printf(“Can’t find file.”); else …

if … statements are used to respond appropriately when the end-of-file mark is found or when the program can’t find a requested file.