Chapter 1 Introduction to C Language

1. Chapter 1 Introduction to C Language By C. Shing ITEC Dept Radford University

2. 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

3. 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

4. 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

5. 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

6. 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

7. Running C Program • C source program -> C Compiler -> Object program -> Link (to get executable program) ->(feed data) Execution

8. 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.out or • gcc -o executable mainfile.c [sub1filename.c sub2filename.c] then • executable

9. 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

10. Program Structures (Cont.) • Compile only (Solaris) • gcc –c filename.c or • cc -c filename.c (traditional C)

11. 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>

12. 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!”

13. 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;

14. 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 }

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

16. 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 ()

17. 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>

18. 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

19. 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;

20. 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; }

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

22. vi/vim editor • vi filename.c • Please refer to http://www.chem.brown.edu/instructions/vi.html

23. Use vi Editor • 2 modes: • Editor mode (press <esc>): make correction • Insert/open/append mode (press<i>/<o>/<a>): add text

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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 • Example 1

31. Programming Environment in .NET • Running C/C++ Instruction (Reference) • Not used in this course

32. 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