2.History of programming language, an introduction

This slide provide history and level of programming language in details.

1. 10/14/20241

2. Language Translator

3. Language Translator
Translators are system programms, which translate programs written
in any high, or assembly language into 1’s and 0’s or machine language.
There are three types of language processors or translators
Assembler
Compiler
Interpreter
Program code
Language
translator
Machine code

4. Assembler
The software that translates assembly code into the computer’s
machine code is called assembler
A program written by a programmer in assembly language is called
source program
After this source code has been converted into object code
Language Translator

5. Complier
A compiler is a computer software that translates a whole program,
called the source code at once into machine code (object code)
Interpreter
An interpreter in another type of translator used for translating a
language program into machine code
It takes one statement of program and translates it into a machine
instruction which is immediately executed by computer
Language Translator

6. TRANSLATION PROCESS
Source Program / code
Target Program / code

7. Programs
•Source Program:
•The program we write in English langue using the editor is called Source
program.
•This program is given to the compiler for translation.
•Target Program:
•The program i.e. produced by the compiler after translating the source
program is called target program.
•This program is in binary form.

8. Variable ,keyword, constant, data type
Variable:
an entity that may change its value during program execution is
called variable.
Keyword:
are words that meaning is already defined to the language.
Constant:
an entity that cant be changed during program execution.
Data type:
are used to show the type of data .

9. Data Type
data type is used to
•Identify the type of a variablewhen the variable is declared
•Identify the type of the return valueof a function
•Identify the type of a parameterpassed to function

10. Data Type (continued)
When the compiler encounters a declaration for a variable, it sets up a
memory location for it
An operator used on a variable or variables is legal only if
The operator is defined in that programming language for a variable
of that type
The variable or variables involved with the operator are of the same
or compatible types

11. Classifications of Data Types
Built-in data types
Fundamental data types (int, char, double,
float, void,bool)
Programmer-defined data types
Structure
Union
Enumeration

12. Fundamental Data Types
void–used to denote the type with no values
int–used to denote an integer type
char–used to denote a character type
float, double–used to denote a floating point type
int *,float *,char*–used to denote a pointer
type, which is a memory address type
bool-boolean values (true,false)

13. Constant & Variable
A constantis an entity or value that does not change during the
execution of a program.
an entity that may vary during program execution is called a variable.
Variablenames are names given to locations in memory.
These locations can contain integer, real or character constants.

14. Rules for Constructing Identifiers in C
The first character in the variable name must be an alphabet(A-Z,a-z)
or underscore.
Capital letters A-Z, lowercase letters a-z, digits 0-9, and the
underscore character
First character must be a letter or underscore
There can be no embedded blanks
Keywords cannot be used as identifiers
Identifiers are case sensitive
No commas or blanks are allowed within a variable name.
No special symbol other than an underscore (as in gross_sal)
can be used in a variable name.
Identifiers refer to the names of data types,
constants, variables, and functions
Example:
si_int
m_hra
pop_e_89

15. C constants can be divided into two major categories
Primary Constant
Secondary Constant
These constants are further categorized as shown in below figure

16. Rules for constructing Integer Constants
An integer constant must have at least one digit
It must not have a decimal point
It can be either positive or negative
If no sign precedes an integer constant, it is assumed to be positive
No commas or blanks are allowed within an integer constant
The allowable range for integer constant is -32768 to 32767
Example: 25, +134, 0, -600

17. Rules for constructing Character Constants
A character constant is a single alphabet, a single digit or a single
special symbol enclosed within single quotes
The maximum length of a character constant can be 1 character
Example:
‘A’, ‘l’, ‘5’, ‘=’, ‘ ’, ‘.’

18. Definitions
Initialization
Declaration
Variable
Constant
Terminator
Data type
Assignment operator
Int a =4;

19. Simple C Program
/* A first C Program*/
#include <stdio.h>
void main()
{
printf("Hello World \n");
}

20. Preprocessor Directives
The first thing to be checked by the compiler.
Starts with ‘#’.
Tell the compiler about specific options that it needs to
be aware of during compilation.
There are a few compiler directives.
#include <stdio.h>
Tell the compiler to include the file stdio.hduring compilation
Anything in the header file is considered a part of the program

21. Simple C Program
Line 1: #include <stdio.h>
As part of compilation, the C compiler runs a program called
the C preprocessor.
The preprocessor is able to add and remove code from your
source file.
In this case, the directive #includetells the preprocessor to
include code from the file stdio.h.
This file contains declarations for functions that the program
needs to use. A declaration for the printffunction is in this file.

22. Simple C Program
Line 2: void main()
This statement declares the main function.
A C program can contain many functions but must always
have one main function.
A function is a self-contained module of code that can
accomplish some task.
The "void" specifies the return type of main. In this case,
nothing is returned to the operating system.

23. Simple C Program
Line 3: {
This opening bracket denotes the start of the program.

24. Simple C Program
Line 4: printf("Hello World From About\n");
Printfis a function from a standard C library that is used to print
strings to the standard output, normally your screen.
The compiler links code from these standard libraries to the code
you have written to produce the final executable.
The "\n"is a special format modifier that tells the printfto put
a line feed at the end of the line.
If there were another printfin this program, its string would
print on the next line.

25. Simple C Program
Line 5: }
This closing bracket denotes the end of the program.

26. Structure of a C program#include <stdio.h>
void main (void)
{
printf(“\nHello World\n”);
}
Preprocessor directive (header file)
Program statement#include <stdio.h>
#define VALUE 10
int global_var;
void main (void)
{
/* This is the beginning of the program */
int local_var;
local_var = 5;
global_var = local_var + VALUE;
printf (“Total sum is: %d\n”, global_var); // Print out the result
}

}Preprocessor directive
Global variable declaration
Comments
Local variable declaration
Variable definition

27. Comments
Explanations or annotations that are included in a
program for documentation and clarification purpose.
Completely ignored by the compiler during compilation
and have no effect on program execution.
Starts with ‘/*’ and ends with ‘*/’
Some compiler support comments starting with ‘//’

28. Statements
A specification of an action to be taken by the computer
as the program executes.
In the previous example, there are 2 lines following
variable declaration and variable definition that
terminate with semicolon ‘;’.
global_var = local_var + VALUE;
printf (“Total sum is: %d\n”, global_var);
Each line is a statement.

29. Basic Functions
A C program consists of one or more functions that contain
a group of statements which perform a specific task.
A C program must at least have one function: the function
main.
We can create our own function or use the functions that has
been created in the library, in which case we have to include
the appropriate header file (example: stdio.h).

30. In this section, we will learn a few functions that are pre-
defined in the header file stdio.h
These functions are:
printf()
scanf()
In addition to those functions, we will also learn about Format
Specifierand Escape Sequencewhich are used with printf()
and scanf().

31. printf()
Used to send data to the standard output (usually the
monitor) to be printed according to specific format.
The general form of printf( ) function is,
printf( “format string", <list of variables> ) ;
<format string> can contain,
%f for printing real values
%d for printing integer values
%c for printing character values
Control string is a combination of text, format specifier and
escape sequence.
Example:
printf(“Thank you”);
printf(“Total sum is: %d\n”, global_var);
%d is a format specifier
\n is an escape sequence

32. scanf()
Read data from the standard input device (usually keyboard) and
store it in a variable.
General format:
scanf(“Control string”, &variable);
The general format is pretty much the same as printf() except that
it passes the address of the variable (notice the &sign) instead of
the variable itself to the second function argument.
Example:
intage;
printf(“Enter your age: “);
scanf(“%d”, &age);

33. Summary
The three primary constants and variable types in C are
integer, floatand character.
A variablename can be of maximum 31 characters.
Do not use a keywordas a variablename.
An expressionmay contain any sequence of constants,
variables and operators.
Input/output in C can be achieved using scanf( ) and
printf( ) functions.