Chapter 1 Introduction to C Language

By C. Shing

ITEC Dept

Radford University

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Objectives Understand brief history of C Describe C components Understand C features Understand Program Structure in C Understand how to run a C program

using GNU C compiler and in .NET environment Understand how to use a vi editor

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C Brief History 1967 Martin Richards

Develop BCPL language for writing OS and compilers 1969 Ken Thompson, Bell Lab

Develop B language for Unix (on DEC PDP-7) machine dependent

1970 Dennis Ritchie, Bell Lab developed C language on DEC PDP-11 (traditional C: cc) machine independent

1978 C++: Bjarne Stroustrup Object-oriented Super-set of C

1989 ANSI C (e.g. GNU C: gcc) 1999 updated ANSI C

Variable-length array Restrict pointer modifier

2002 Microsoft C# for .NET framework

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C Components Compiler

traditional ANSI

Preprocessor: code begins with # at column 1 Process code before compiler starts translating

Library Standard Library (/usr/lib/libc.a)

Examine table of contents: ar t /usr/lib/libc.a Math Library (/usr/lib/libm.a) Utility Library

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C Features Middle-level language

Can access bit level Machine independent Case sensitive Type language (weak type)

Variable must be declared a type Allow automatic type conversion No boolean data type (0: false, non-zero: true)

No run-time error checking Programmer’s responsibility: array boundary

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C Features Small language, very efficient

32 keywords in ANSI C compared to BASIC

(> 100 reserved words) All subprograms are functions Function uses pass-by-value Function cannot be nested within another function

Can manipulate memory System programming tool

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Running C Program C source program -> C Compiler

-> Object program -> Link

(to get executable program)

->(feed data) Execution

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Program Structures File Extension

.c (or .cpp for C++) Compile & link (Solaris) , then execute

gcc mainfile.c [sub1filename.c sub2filename.c]or in traditional C: (if math library is called in the

program) cc mainfile.c [sub1filename.c sub2filename.c] –lm

then a.outor gcc -o executable mainfile.c

[sub1filename.c sub2filename.c] then executable

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Program Structures (Cont.) Compile & link (Solaris) to your library, then execute

gcc mainfile.c [sub1filename.c sub2filename.c]-lyourlibraryname

or in traditional C: (if yourlibrary is called in the program) cc mainfile.c [sub1filename.c sub2filename.c]

–llyourlibrarynamethen a.outor gcc -o executable mainfile.c [sub1filename.c sub2filename.c] –llyourlibraryname then executable

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Program Structures (Cont.) Compile only (Solaris)

gcc –c filename.c

or cc -c filename.c (traditional C)

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Program Structures (Cont.) mainfile.c/* *********************************** This is a comment ** Block ************************************/// Comment line// Declaration for standard library: in

/usr/include/stdio.h // The following line is required#include <stdio.h>

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Program Structures (Cont.)

#include <math.h> //if math library is used

// The following file yourdeclaration.h

// is in your current directory

#include “yourdeclaration.h”

// define macro constants

#define PI 3.14159

#define MY_MESSAGE “Good Morning!”

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Program Structures (Cont.)// declare named global constantsconst int number = 4;

// declare typestypedef char myCharacter;

// declare global variablesint a;char b=‘a’, c=‘\n’;myCharacter e;long d = 14000L; // this means long int (default int)float x=-2.5F;double y=2.5;

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Program Structures (Cont.)// declare function prototypeint sub1(int);

// define main functionint main (void){ // declare local variables int lb, lc;

lc = 2; // call function lb = sub1(lc); printf(“%d\n”,lb);

return 0; // no error exit}

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Program Structures (Cont.)// define functionint sub1 (int l){ // declare local variables int la; // call function la = 5*l;

return la; }

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Appendix: Traditional C (not recommended to write)

No const data type (use #define instead) No void data type Main function does not return anything No function prototype Return type for function default is int if not

specified Function formal parameters are defined after ()

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Program Structures (Traditional C) mainfile.c/* *********************************** This is a comment ** Block ************************************/// Comment line// Declaration for standard library: in

/usr/include/stdio.h // The following line is required#include <stdio.h>

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Program Structures (Cont.)

#include <math.h> //if math library is used

// The following file yourdeclaration.h

// is in your current directory

#include “yourdeclaration.h”

// define macro constants

#define PI 3.14159

#define MY_MESSAGE “Good Morning!”

#define NUMBER 4

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Program Structures (Cont.)

// declare types

typedef char myCharacter;

// declare global variables

int a;

char b=‘a’, c=‘\n’;

myCharacter e;

long d = 14000L;

float x=-2.5F;

double y=2.5;

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Program Structures (Cont.)// define function sub1 must appear before main functionsub1 ()int l;{ // declare local variables int la; // call function la = 5*l;

return la; }

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Program Structures (Cont.)// define main functionmain (){ // declare local variables int lb, lc; lc = 2; // call function lb = sub1(lc); printf(“%d\n”,lb);}

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vi/vim editor vi filename.c Please refer to

http://www.chem.brown.edu/instructions/vi.html

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Use vi Editor 2 modes:

Editor mode (press <esc>): make correction Insert/open/append mode

(press<i>/<o>/<a>): add text

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Use vi Editor (Cont.) Editor mode: (Common keys)

<h>:move left, <l>: move right,

<j>: move down, <k>: move up <0>: beginning of line, <$>: end of line <w>: next word, <b>: previous word <:><n>: go to line n

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Use vi Editor (Cont.) Editor mode: (Cont.)

<x>: delete character, <d><w>: delete word <d><d>: delete line (to clip board), <Y>: copy line <p>: paste from clip board after/below cursor <P>: paste from clip board before/above cursor Move cursor to line m,<d><d>, then move cursor to line n, <p>: move line m to below line n Move cursor to line m,<Y>, then move cursor to line n, <p>: copy line m to below line n

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Use vi Editor (Cont.) Editor mode: (Cont.) Note: put a number n before an action will

repeat the action n times.For example:10<j>: move cursor down 10 lines10<x> delete 10 characters10<d><d>: delete 10 lines10<Y>: copy 10 lines

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Use vi Editor (Cont.) Editor mode: (Cont.)

<r>: replace a character <c><w> type in word<esc>: replace a word <R> type in words<esc>: replace/type over words </>type in word<enter>: search the 1st occurrence of the word <:><w>: save, <:><w><q>: save and quit, <:><w><q>type in filename<enter>: save to filename and quit <:><s></><word1></><word2></><enter>: substitute the 1st occurrence of word1 for word2 <:><1><,><$><s></><word1></><word2></><enter>: substitute word1 for word2 from line 1 to lat line

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Use vi Editor (Cont.) Editor mode: (Cont.)

<J>: join the cursor line and the line below into one line Move cursor to position <i><esc>:

split at the cursor position into 2 lines <.>: repeat the previous command <n>: next searched word <G>: go to last line <ctrl><g>: file status

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Use vi Editor (Cont.) Insert/open/append mode: (Common keys)

<i>type in words<esc>:insert words before the cursor

<a>type in words<esc>:append words after the cursor

<o>type in words<esc>:open lines after the cursor

and append words <O>type in words<esc>:open lines before the cursor

and append words

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Class Example Hands On Example0:

edit the following 2 lines in file .exrc (vi ~/.exrc) :abbr #b /************************ :abbr #e ************************/

Then when you usevi template.c

And after press<i>/<a>/<o> to insert text, you type#b followed by <Enter>, you add a line /******** in.

Similarly, when you type #e followed by <Enter>, you add a line ********/ in

Example 1

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Programming Environment in .NET Running C/C++ Instruction (Reference)

Not used in this course

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Reference: Brian W. Kernighan & Dennis M. Ritchie:

C Programming Language, ANSI Edition

Prentice Hall Al Kelley & Ira Pohl: A Book on C, 4th ed.

Addison Wesley Deitel & Deitel: C How to Program, 4th ed.,

Chapter 1, Prentice Hall