CSCI 130

Chapter 1

History of C

• Bell Telephone Laboratories (1972)

• Dennis Ritchie (also created UNIX)

• A - B - C

Initially Many Versions

• Incompatibility

• ANSI– American National Standards Institute

• ANSI Standard C

Advantages of C

• Powerful, Flexible– Operating Systems– Applications software– Compilers

• Popular

• Portable

• Modular (should be written in functions)

Problem Solving Technique

• Define Problem

• Devise plan to fix problem

• Implement the plan

• Test

Necessary Information

• Is computer program required?

• Inputs/Outputs

• Formulas

• Organization (flow of logic)

Ex: Find area of a circle

• Is computer required?

• Inputs / Outputs– Need the radius of circle as input– Area will be the output

• Formulas– Area = pi * radius ^ 2

Find area of circle - continued

• Flow of logic:– Request radius of circle– Calculate area = pi * radius ^ 2– Output area

Steps in C programming cycle

• Use editor to create source code

• Compile source code into object code

• Link object file into executable file

• Execute file

Use editor to create source code

• Any editor can be used– Editor supplied with language

• Any text based editor

• DOS editor

• Notepad

• Write program following syntax of language

• Save file as: filename.c

Compile Source Code

• Different compilers use different commands

• Most (such as Borland, Code Warrior) have IDE - can compile via GUI interface

• Process creates a new file: filename.obj

• This file is object code - in format readable by machine

Link object file

• Most compilers will do this via GUI interface as well (may combine compiling and linking)

• Links internal C library functions (such as printf, scanf) with source code

• Creates new file: filename.exe

Execute Program

• Program can now be executed– Type filename at DOS prompt– Most compilers allow program to be run via

GUI interface• may combine compiling, linking, and running

• Finished product can be shared– source code does not have to be shared