1. Introduction to C Programming
Lecture 2

2. Today’s Lecture Software Categories System Software
Application Software
Introduction to ‘C’ Language
History
Evolution
Justification
Development Environment of ‘C’

3. There are two main categories of software
System software
Application Software

4. Technology Without An Interesting Name
TWAIN
Technology Without An Interesting Name

5. Evolution of programming languages
The lack of portability between different computers led to the development of high-level languages—so called because they permitted a programmer to ignore many low-level details of the computer's hardware
Details of procedural, non-procedural will follow in the lectures

6. How people used to program
Machine Language….. Damn! It was difficult
Assembly Language…. Remember ADD?
Required too much user involvement
To much to remember
Less semantic
C Language
B Language.. Bell Labs
Improved to C Language
Is a compiled language

7. ANSI C

8. Tools of the trade
Editor
Interpreter and Compilers
Debuggers

9. Integrated Development Environment (IDE)
It contains
Editor
Compilers
Debugger
Linkers
Loaders

10. Loader puts program in memory.
Preprocessor program
processes the code.
Loader puts program in memory.
CPU takes each
instruction and executes it, possibly storing new data values as the program executes.
Compiler creates object code and stores it on disk.
Linker links the object
code with the libraries
Loader
Primary Memory
Compiler
Editor
Preprocessor
Linker .
Disk
CPU
Program is created in the editor and stored on disk.

11. #include <iostream.h>
main ( ) {
cout << “ Welcome to NIIT “; }

12. Variable X
Variable

13. Variable
Pic of the memory 25
10323
name
of the variable

14. Variable
Variable starts with
Character
Underscore _ (Not Recommended)

15. Variable
Small post box X

16. Variable
Variable is the name of a location in
the memory
e.g. x= 2;

17. Variable
In a program a variable has:
Name
Type
Size
Value

18. Assignment Operator =
x = 2 X 2

19. Assignment Operator L.H.S = R.H.S. X+ 3 = y + 4 Wrong Z = x +4
x +4 = Z Wrong

20. 10 X
X = 10 ;
X = 30 ; 30 X

21. X = X + 1; X 10
+ 1 = 11 X

22. Data type i
int i ; //Declaration line

23. Writing C program

24. Examples of C/C++ compilers of today:
Compiler converts human readable language to a language which is understandable by the operating system/hardware
Examples of C/C++ compilers of today:
Visual C++
GCC/G++
DJGPP (open source for windows like GCC)
Borland C
Turbo (obsolete and not recommended)

25. 3 Stages of Compilation Stage 1: Preprocessing
Performed by a program called the preprocessor
Modifies the source code (in RAM) according to preprocessor directives (preprocessor commands) embedded in the source code
Strips comments and white space from the code
The source code as stored on disk is not modified.

26. 3 Stages of Compilation (con’t)
Stage 2: Compilation
Performed by a program called the compiler
Translates the preprocessor-modified source code into object code (machine code)
Checks for syntax errors and warnings
Saves the object code to a disk file, if instructed to do so (we will not do this).
If any compiler errors are received, no object code file will be generated.
An object code file will be generated if only warnings, not errors, are received.

27. Object code:
It is machine language code containing various calls specific to operating system… e.g the object code written by compiler is not only hardware dependent but also operating system dependent.
So if you have linux and windows both operating systems then object file of compiled by one Operating System (OS) will not get executed on the other OS

28. 3 Stages of Compilation (con’t)
Stage 3: Linking
Combines the program object code with other object code to produce the executable file.
The other object code can come from the Run-Time Library, other libraries, or object files that you have created.
Saves the executable code to a disk file. On the Linux system, that file is called a.out.
If any linker errors are received, no executable file will be generated.

29. Program Development Using gcc
Editor
Source File pgm.c
Preprocessor
Modified Source Code in RAM
Compiler
Program Object Code File pgm.o
Other Object Code Files (if any)
Linker
Executable File a.out

30. #include <iostream.h> //This is pre-processor directive
void main ( ) //this tells the starting point of your program {
int x ;
int y ;
int z ;
x = 10 ;
y = 20 ;
z = x + y ;
cout << " x = " ; //print the text on monitor
cout << x ;
cout << " y = " ;
cout << y ;
cout << " z =x + y = " ;
cout << z ; }

31. int x, y, z ;
int x; int y; int z ;

32. Data Types
int
short
long
float
double
char

33. Arithmetic operators
Plus +
Minus -
Multiply *
Divide /
Modulus %

34. Arithmetic operators
i + j
x * y
a / b
a % b

35. % = Remainder
5 % 2 = 1
2 % 2 = 0

36. 4 / 2 = 2
5 / 2 = ?

37. Precedence
Highest: ( )
Next: * , / , %
Lowest: + , -

38. Another C++ Program /*****************************************
** File: proj1.c
** Author: Joe Student
** Date: 9/15/01
** SSN:
** Section: 0304 ** **
** This program prompts the user for two integer values then displays
** their product.
***********************************************/

39. Another C Program (con’t)
#include <stdio.h>
int main( void ) {
int value1, value2, product ;
cout<<“Enter two integer values: ;
cin>>value1>>value2;
product = value1 * value2 ;
cout<<“Product = ”<<product ;
return 0 ; }

40. Tokens The smallest element in the C language is the token.
It may be a single character or a sequence of characters to form a single item.

41. Tokens are: Tokens can be: Numeric constants Character constants
String constants
Keywords
Names (identifiers)
Punctuation
Operators

42. Numeric Constants
Numeric constants are an uninterrupted sequence of digits (and may contain a period). They never contain a comma.
Examples:
123
98.6

43. Character Constants Singular! One character defined character set.
Surrounded on the single quotation mark.
Examples:
‘A’
‘a’
‘$’
‘4’

44. String Constants
A sequence characters surrounded by double quotation marks.
Considered a single item.
Examples:
“UMBC”
“I like ice cream.”
“123”
“CAR”
“car”

45. Keywords Sometimes called reserved words.
Are defined as a part of the C language.
Can not be used for anything else!
Examples:
int
while
for

46. Names Sometimes called identifiers.
Can be of anything length, but on the first 31 are significant (too long is as bad as too short).
Are case sensitive:
abc is different from ABC
Must begin with a letter and the rest can be letters, digits, and underscores.
Must follow the standards for this course!

47. Punctuation
Semicolons, colons, commas, apostrophes, quotation marks, braces, brackets, and parentheses.
; : , ‘ “ [ ] { } ( )

48. Operators There are operators for: assignments mathematical operations
relational operations
Boolean operations
bitwise operations
shifting values
calling functions
subscripting
obtaining the size of an object
obtaining the address of an object
referencing an object through its address
choosing between alternate subexpressions