Chapter 5: Preparing C Programs

Program development Understanding the problem EDIT Writing an algorithm Converting to code COMPILE RUN errors Result Verifying the algorithm Chapter 5 Program development

Program development pico prog.c cc prog.c a.out Source code EDIT COMPILE RUN errors Result Source code pico prog.c cc prog.c a.out Chapter 5 Program development

High-level languages Machine language: computer’s native language. Add two numbers: 00100111 1010 0101 Assembly language: uses mnemonics. Add two numbers: ADD R1 R2 An assembly code needs to be translated to machine code. Chapter 5 High-level languages

High-level languages High-level programming languages: bridging the gap between machine language and natural languages. Examples: COBOL, Fortran, Algol, C Add two numbers (in C): Z = A + B; Compilation: translation to machine code. Chapter 5 High-level languages

A C program A sample C program /* A simple C program to read a number & compute and display its square by using the multiplication (*) operator. */ #include <stdio.h> main () /* a C program always has a main function */ { int n; /* this declares an integer variable 'n' */ printf ("\nEnter the number to be squared: "); scanf ("%d", &n); printf ("Using the * operator, the square of %d is %d.\n\n", n, n*n); } Chapter 5 A C program

Compilation in C Use the cc or gcc compiler: cc prog.c Produces executable file a.out if no errors To specify name of executable file, use -o option: cc -o prog prog.c Name of executable file becomes ‘prog’. Chapter 5 Compilation in C

Errors Compilation errors: occur during compilation. Reason: syntax errors. Easy to rectify. Run-time errors: occur during execution. Reasons: logic errors, data errors, computation errors. Harder to rectify. Chapter 5 Errors

Homework Try exercises in chapter 5. Chapter 5 Homework