Lesson 2

• C - is a general-purpose programming language which features economy of expression, modern control flow and data structures and a rich set of operations.
• C has been called as “system programming language” because it is useful for writing compilers and operating systems.
• Basic Combined Programming Language (BCPL) is developed by Martin Richards in 1967. This language is turn strongly influenced the development of the next language –B.
• B is written and developed by Ken Thompson in 1970 for the first UNIX system on the DEC PDP-7. Both BCPL and B are “typeless” languages.
• C is an expansion of B. A programming language designed by Dennis Ritchie in 1972 at AT and T Bell Laboratories. C was originally designed for and implemented on the UNIX operating system on the DEC PDP-II. The new C added something that B did not have data types.
• Turbo C is a version of C developed by Borland International Corporation in 1987. This version is designed to run on various microcomputer systems, namely those which use the operating system MS-DOS, the operating system for the IBM Personal Computers and Compatibles.
• Interpreter reads the source code of your program one line at a time and performs the specific instructions contained in that line.
• Compiler reads the entire program and converts it into object code-the form that can be directly executed by the computer.
• Compile Time refers to the events that occur during the compilation process.
• Object Code is a translation of the program source code in a form that can be directly executed by the computer. It is also called the binary code and machine code.
• Source Code is the text of a program that a user can read; commonly thought of as a program.
• Run Time refers to the events that occur while the program is executing.
• Library is the collection of pre-written.
• Syntax errors are detected during compiled time.
• Semantic/ Run – Time errors are detected during execution-time.
• Editor is used to create program source code.
• Extended C language. This version of C is significantly extended from the “base bone” language of Ritchie’s specifications. The extension includes enhancement which make the Turbo C compatible with the new proposed and ANSI Standard.
• Compiler is used to convert source code into machine code or binary code.
• Debugger - is used for testing program and locating programming errors.
• Run – Time Environment is the capability for running programs within the Turbo C system.
• User Interface -The various features of Turbo C are integrated into a single program which allows you to smoothly proceed from source – code entry to compilation to debugging to running without ever leaving the Turbo C environment.
• Identifiers - is names that are used to reference variables, functions, labels, and various other user-defined object; sequence of letters, digits and the special character-, which is called an underscore.
• int variables - is whole number consisting of an optional sign (+ or -) followed by a sequence of digit. It cannot contain commas. Variables of this type are often used for controlling loops and conditional statements.
• float - consists of an optional sign (+ or -), followed by one or more digits, a decimal point, and or one or more further digits. It occupies 4 bytes. It can include an optional exponent ranging from 3.4 E to -38 to 3.4 E +38
• double (double precision) - is a special float which can store more significant digits and have a longer exponent. It occupies 8 bytes in the memory. It ranges from 1.7 E – 308 to 1.7 E +308
• char - is a single letter, digit, punctuation mark or control symbol recognized by the computer. Written enclosed within single quotation marks, but literals string are enclosed in double quotation marks . A character may be assigned an integer value between -128 and +127. Unsigned char data type may be assigned an integer value from 0 to 255.
• void - valueless
• Three uses of void: 1. To declare explicitly a function as returning no value. 2. To declare explicitly a function having no parameters. 3. To create generic pointers.
• Variables are identifiers which can be assigned a value within a program. It has 32 valid characters, and these are letters, digits, and underscore.
• A declaration is used to name an object such as variables.
• Variables initialization - The process of assigning starting values to the variables
• It is important to remember that variables are not initialized automatically. When variable is defined they usually contain garbage, so we need to initialize them or store data in them before accessing their values.
• Global Variables are initialized only at the start of the program. All global variables are initialized to zero if no other initializer is specified.
• Local Variables are initialized each time the function in which they are declared is entered.
• Constants refer to fixed values that may not be altered by the program. Turbo C constant can be any of the basic data types or known as Literal Constants.
• String constant or Literal string constant - consists of a phrase contained/enclosed within double quotes. It is used in printf statements to introduce text messages into a program.
• Declared Constants which are assigned a name Declared constant are defined using a # defined declaration at the beginning of the program. This declaration is introduced by the word # defined follow by a constant name and its value.
• const -Variables declared under this modifier can not be changed during program execution. However, you may give an initial value before the start of the program.
• The # define declaration is used at the beginning of the program. Like const, it is also used in declaring constants.
• A modifier - is used to alter the meaning of the base type to more precisely fit the needs of various situation. With the exception of type void, the basic data type may have various modifiers preceding them.