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c unit -1. data btypes, variables,operators
- 1. programming language • programming language is the medium of communication between you (a person) and a computer system. It is the set of some instructions written in a specific style (coding) to instruct the computer to do some specific task • Types of computer programming languages There are basically three types of computer programming languages, they are • 1. Low level programming languages • 2. High level programming languages • 3. Middle level programming languages
- 2. programming language 1) Low level programming languages:These are machine dependent programming languages such as Binary (Machine code) and Assembly language. Advantages of machine level language: • Machine level languages are directly interacting with computer system. • There is no requirement of software of conversion like compiler or interpreters. • It takes very less time to execute a program, because there is no conversion take place. Disadvantages of machine language: • Its machine dependent language i.e. individual program required for each machine. • To develop a program in machine language, it's too hard to understand and program.
- 3. 2) Middle Level programming language • the programming languages which have features of Low Level as well as High Level programming languages known as "Middle Level" programming language. Advantages of Assembly language: • It is easily understood by human because it is uses statements instead of binary digits. • To develop a program it takes less time. • Debugging and troubleshoot is easy due to easily find error. Disadvantages of Assembly language: • It's a machine dependent language due to that program design for one machine no use of other machine. • Sometime it's hard to understand the statement or command use.
- 4. 3) High level programming languages • High level languages are third generation languages . They are written in english language. Examples are • C,C++,JAVACOBOL Advantages of high level language: • In this instructions and commands much easier to remember by programmer. • Its logic and structure are much easier to understand. • Debugging is easier compare to other languages. • Less time consuming to writing new programs. • HLL are described as being portable language. Disadvantages of high level language: • HLL programming language take more space compare to other MLL (machine level language) and/or ALL (Assembly level language). • This programming language execute slowly.
- 5. HISTORY OF C LANGUAGE • C is a structured programming language developed by Dennis Ritchie in 1973 at Bell Laboratories. It is one of the most popular computer languages. • Clanguage has evolved from three different structured language ALGOL, BCPL and B • It uses the many concepts like data types,variables,functions etc. • Programs written in C language takes very less time to execute and almost executes at the speed of assembly language instructions. • Initially C language was mainly used for writing system level programs, like designing operating systems, but there are other applications as well which can be very well designed and developed using C language, like Text Editors, Compilers, Network Drivers etc
- 6. HISTORY OF C LANGUAGE
- 7. Basic Structure • C program can be viewed as a group of building blocks called functions. • A function is a subroutine that may include one or more statements designed to perform a specific task. • To write a C program, we first create functions and then put them together. • A C program may contain one or more sections
- 9. Basic Structure • 1. Documentation Section This section consists of comment lines which include the name of the program, the name of the programmer, the author and other details like time and date of writing the program. Documentation section helps anyone to get an overview of the program. • 2. Link Section The link section consists of the header files of the functions that are used in the program. It provides instructions to the compiler to link functions from the system library such as using the #include directive. • #include<stdio.h> //link section • #include<conio.h> //link section • 3. Definition Section All the symbolic constants are written in the definition section. Macros are known as symbolic constants. #define PI 3.14 //definition section • 4. Global Declaration Section The global variables that can be used anywhere in the program are declared in the global declaration section. This section also declares the user defined functions. float area; //global
- 10. Basic Structure • 5)Funtion prototype and declaration section: It gives information about the function like return type,parameter names used inside the functions. • 6. main() Function Section It is necessary to have one main() function section in every C program. This section contains two parts, declaration and executable part. The declaration part declares all the variables that are used in executable part. These two parts must be written in between the opening and closing braces. Each statement in the declaration and executable part must end with a semicolon (;). The execution of the program starts at opening braces and ends at closing braces. • 7)user defined functions: user can define his own funtions here
- 11. Rules to Write a C program • All lines of C statements must end with a semicolon. 1. C is case-sensitive. That is, uppercase and lowercase characters are different. Usually, the statements are typed in lowercase. 2. A C Program statement can be split into many lines or can be written in one line. 3. Braces must always match upon pairs, i.e., every opening brace {must have a matching closing brace}. 4. All C program starts with main( ) function.