Chapter 1 Introduction to C
Language
By C. Shing
ITEC Dept
Radford University
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

Slide 2
C Brief History
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1967 Martin Richards
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1969 Ken Thompson, Bell Lab
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Object-oriented
Super-set of C
1989 ANSI C (e.g. GNU C: gcc)
1999 updated ANSI C
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developed C language on DEC PDP-11 (traditional C: cc)
machine independent
1978 C++: Bjarne Stroustrup
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Develop B language for Unix (on DEC PDP-7)
machine dependent
1970 Dennis Ritchie, Bell Lab
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Develop BCPL language for writing OS and compilers
Variable-length array
Restrict pointer modifier
2002 Microsoft C# for .NET framework
Slide 3
C Components
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Compiler
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Preprocessor: code begins with # at column 1
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traditional
ANSI
Process code before compiler starts translating
Library
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Standard Library (/usr/lib/libc.a)
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Examine table of contents: ar t /usr/lib/libc.a
Math Library (/usr/lib/libm.a)
Utility Library
Slide 4
C Features
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Middle-level language
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Machine independent
Case sensitive
Type language (weak type)
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Can access bit level
Variable must be declared a type
Allow automatic type conversion
No boolean data type (0: false, non-zero: true)
No run-time error checking
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Programmer’s responsibility: array boundary
Slide 5
C Features
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Small language, very efficient
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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
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System programming tool
Slide 6
Running C Program
C source program -> C Compiler
-> Object program -> Link
(to get executable program)
->(feed data) Execution
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Slide 7
Program Structures

File Extension
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
.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.out
or
 gcc -o executable mainfile.c
[sub1filename.c sub2filename.c]
then
 executable
Slide 8
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]
–llyourlibraryname
then
 a.out
or
 gcc -o executable mainfile.c
[sub1filename.c sub2filename.c] –llyourlibraryname
then
 executable
Slide 9
Program Structures (Cont.)

Compile only (Solaris)
 gcc –c filename.c
or
 cc -c filename.c (traditional C)
Slide 10
Program Structures (Cont.)
 mainfile.c
/*
**********************************
* This is a comment
*
* Block
*
**********************************
*/
// Comment line
// Declaration for standard library: in /usr/include/stdio.
// The following line is required
#include <stdio.h>
Slide 11
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!”
Slide 12
Program Structures (Cont.)
// declare named global constants
const int number = 4;
// declare types
typedef char myCharacter;
// declare global variables
int 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;
Slide 13
Program Structures (Cont.)
// declare function prototype
int sub1(int);
// define main function
int main (void)
{
// declare local variables
int lb, lc;
lc = 2;
// call function
lb = sub1(lc);
printf(“%d\n”,lb);
return 0; // no error exit
}
Slide 14
Program Structures (Cont.)
// define function
int sub1 (int l)
{
// declare local variables
int la;
// call function
la = 5*l;
return la;
}
Slide 15
Appendix:
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Traditional C (not recommended to write)
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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 ()
Slide 16
Program Structures (Traditional C)
 mainfile.c
/*
**********************************
* This is a comment
*
* Block
*
**********************************
*/
// Comment line
// Declaration for standard library: in /usr/include/stdio.
// The following line is required
#include <stdio.h>
Slide 17
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
Slide 18
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;
Slide 19
Program Structures (Cont.)
// define function sub1 must appear before main function
sub1 ()
int l;
{
// declare local variables
int la;
// call function
la = 5*l;
return la;
}
Slide 20
Program Structures (Cont.)
// define main function
main ()
{
// declare local variables
int lb, lc;
lc = 2;
// call function
lb = sub1(lc);
printf(“%d\n”,lb);
}
Slide 21
vi/vim editor
vi filename.c
 Please refer to
http://www.chem.brown.edu/instructions/vi.html
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Slide 22
Use vi Editor
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2 modes:
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Editor mode (press <esc>): make correction
Insert/open/append mode
(press<i>/<o>/<a>): add text
Slide 23
Use vi Editor (Cont.)
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Editor mode: (Common keys)
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<h>:move left, <l>: move right,
<j>: move down, <k>: move up
<0>: beginning of line, <$>: end of line
<w>: next word, <b>: previous word
<:><n>: go to line n
Slide 24
Use vi Editor (Cont.)
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Editor mode: (Cont.)
<x>: delete character, <d><w>: delete word
 <d><d>: delete line (to clip board), <Y>: copy line
 <p>: paste from clip board after/below cursor
 <P>: paste from clip board before/above cursor
 Move cursor to line m,<d><d>, then move
cursor to line n, <p>: move line m to below line n
 Move cursor to line m,<Y>, then move
cursor to line n, <p>: copy line m to below line n
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Slide 25
Use vi Editor (Cont.)
Editor mode: (Cont.)
 Note: put a number n before an action will repeat
the action n times.
For example:
10<j>: move cursor down 10 lines
10<x> delete 10 characters
10<d><d>: delete 10 lines
10<Y>: copy 10 lines
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Slide 26
Use vi Editor (Cont.)
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Editor mode: (Cont.)
<r>: replace a character
 <c><w> type in word<esc>: replace a word
 <R> type in words<esc>: replace/type over words
st
 </>type in word<enter>: search the 1 occurrence of the word
 <:><w>: save, <:><w><q>: save and quit,
 <:><w><q>type in filename<enter>: save to filename and quit
 <:><s></><word1></><word2></><enter>:
substitute the 1st occurrence of word1 for word2
 <:><1><,><$><s></><word1></><word2></><enter>:
substitute word1 for word2 from line 1 to lat line
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Slide 27
Use vi Editor (Cont.)
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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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Slide 28
Use vi Editor (Cont.)
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Insert/open/append mode: (Common keys)
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<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
Slide 29
Class Example
Hands On Example0:
edit the following 2 lines in file .exrc (vi ~/.exrc)
:abbr #b /************************
:abbr #e ************************/
Then when you use
vi 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
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Example 1
Slide 30
Programming Environment in .NET
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Running C/C++ Instruction (Reference)
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Not used in this course
Slide 31
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
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Slide 32