1.Header file section:-Header file is defined at start of program.It is defined at head of program so it is called as header file.the name of header file is followed by "extention.h".The ".h" means header.The header file begins with # (hash or sharp) symbol.
e.g stdio.h is file used for standerd input/output function.Some of functions defined in this file are "scanf(), printf(), fscanf(), fopen(), fclose(), fof()".
e.g conio.h is file used for console input/output functions.Some of the functions defined in this file are "getch(), clerscr()".
e.g stdlib.h is used as standard library function.It contain "malloc(), calloc(), toupper(), tolower() functions"
e.g math.h is a file containing mathematical function.It contain "sqrt(), pow(), floor(), ceil(), sin(), cos()" functions.

2. Name of a program:- It is used to indicate the purpose of program.It indicate what is problem to be solved by program.It is given using comment operator at start of program.It is optional.

3.Main function:- The main function contain keyword main().It is indication to the compiler that program execution will be start from main().So main() is starting point of any program.There is only one main() in a c program.In main() function the logic of program is written.All statements and logic is written between pair of curly brackets{}.

4.Declaration part:- This part is used to declare variables of different data types.Initialization of variable is also done in this section.By initialization , we assign starting value to variables.

5.Executable part:- This part follows declaration part.In this part set of statements performing various, functions are defined.There can be single statement or  set of statements.Single statement can be written without curly brackets({}).Compound statements are are written using pair of curly brackets({}).

6.User defined function:- The function defined by user is called as user defined functions.These function are generally defined after main() function.There can be any number of user defined functions but there is only one main function.The body of these functions can be defined before main() function also.If body of functions is defined after main then prototype of function is defined above body of main() function.

7.Comments:-The comments are not necessary.But for good documentation these are added.Comment can be inserted anywhere in program.These are given by writing text between \*   and   * \.

Delimiters : Special type of symbols used for special purpose is called as delimiter.
e.g.
colon                   :
semi colon            ;
parenthesis          ( )
hash                     #
comma                 ,
square bracket     []


SAMPLE OF A 'C' PROGRAM :-

#include<stdio.h>
#include<conio.h>
main()
{
          int a,b,c;
           a=5;
           b=6;
           c=a+b;
           printf("The value of c= %d",c);
           getch();
}

OUTPUT :_

c=11
Download area.......
Download TCC

Program written in c are very efficient and fast. This is due to its variety of data types and powerful operators. It is many time faster than BASIC. This helps developers in saving their valuable time.
• C is a powerful and flexible language which helps system developers to deliver various complex tasks with ease. C is used for diverse projects as operating systems, word processors, graphics, spreadsheets, and even compilers for other languages.
• C is popular among professional programmers for programming, as a result, a wide variety of C compilers and helpful accessories are available.
• C is highly portable language. This means that a C program written for one computer system (an IBM PC, for example) can be run on another system (a DEC VAX system, perhaps) with little or no modification. Portability is enhanced by the ANSI standard for C, the set of rules for C compilers.
• C’s another striking feature is its ability to extend itself. A C program is basically a collection of various function supported by C library (also known as header files). We can also add our own functions to the C library. These functions can be reused in other applications or programs by passing pieces of information to the functions, you can create useful, reusable code.
• Writing C program with user-defined functions makes program more simple and easy to understand. Breaking a problem in terms of functions makes program debugging, maintenance and testing easier.
C has good interface with UNIX OPERATING SYSTEM.
C provide facility of dynamic allocation and deallocation of memory very fast.Pointer make memory related operation.
Facility of structure in C language make DBMS applications like:(a) maintenance of student records.
(b) maintenance of bank records.
(c) storing of employees related information.
As these features shows that C is an excellent choice for your first programming language.

Basic PC shortcut keys

Shortcut Keys	Description
Alt + F	File menu options in current program.
Alt + E	Edit options in current program
F1	Universal Help in almost every Windows program.
Ctrl + A	Select all text.
Ctrl + X	Cut selected item.
Shift + Del	Cut selected item.
Ctrl + C	Copy selected item.
Ctrl + Ins	Copy selected item
Ctrl + V	Paste
Shift + Ins	Paste
Home	Goes to beginning of current line.
Ctrl + Home	Goes to beginning of document.
End	Goes to end of current line.
Ctrl + End	Goes to end of document.
Shift + Home	Highlights from current position to beginning of line.
Shift + End	Highlights from current position to end of line.
Ctrl + Left arrow	Moves one word to the left at a time.
Ctrl + Right arrow	Moves one word to the right at a time.

F1 through F12 keys?

• Almost always used as the help key, almost every program will open the help screen when this key is pressed.
• Enter CMOS Setup.
• Windows Key + F1 would open the Microsoft Windows help and support center.
• Open the Task Pane.

• In Windows commonly used to rename a highlighted icon or file.
• Alt + Ctrl + F2 opens a new document in Microsoft Word.
• Ctrl + F2 displays the print preview window in Microsoft Word.
• Enter CMOS Setup.

• Often opens a search feature for many programs including Microsoft Windows.
• In MS-DOS or Windows command line F3 will repeat the last command.
• Shift + F3 will change the text in Microsoft Word from upper to lower case or a capital letter at the beginning of every word.

• Open find window.
• Repeat the last action performed (Word 2000+)
• Alt + F4 will close the program currently active in Microsoft Windows.
• Ctrl + F4 will close the open window within the current active window in Microsoft Windows.

• In all modern Internet browsers pressing F5 will refresh or reload the page or document window.
• Open the find, replace, and go to window in Microsoft Word.
• Starts a slideshow in PowerPoint.

• Move the cursor to the Address bar in Internet Explorer and Mozilla Firefox.
• Ctrl + Shift + F6 opens to another open Microsoft Word document.

• Commonly used to spell check and grammar check a document in Microsoft programs such as Microsoft Word, Outlook, etc.
• Shift + F7 runs a Thesaurus check on the word highlighted.
• Turns on Caret browsing in Mozilla Firefox.

• Function key used to enter the Windows startup menu, commonly used to access Windows Safe Mode.

• Opens the Measurements toolbar in Quark 5.0.

• In Microsoft Windows activates the menu bar of an open application.
• Shift + F10 is the same as right-clicking on a highlighted icon, file, or Internet link.
• Access the hidden recovery partition on HP and Sony computers.
• Enter CMOS Setup.

• Full-screen mode in all modern Internet browsers.
• Ctrl + F11 as computer is starting to access the hidden recovery partition on many Dell computers.
• Access the hidden recovery partition on eMachines, Gateway, and Lenovo computers.

• Open the Save as window in Microsoft Word.
• Shift + F12 save the Microsoft Word document.
• Ctrl + Shift + F12 prints a document in Microsoft Word.

 Earlier IBM computers also had F13 - F24 on the keyboards. However, because these keyboards are no longer used they are not listed on this page.

Top 10 keyboard shortcuts everyone should know

A History of Information Technology and Systems

• Four basic periods
  Characterized by a principal technology used to solve the input, processing, output and communication problems of the time:
  1. Premechanical,
  2. Mechanical,
  3. Electromechanical, and
  4. Electronic

A. The Premechanical Age: 3000 B.C. - 1450 A.D.

1. Writing and Alphabets--communication.
   1. First humans communicated only through speaking and picture drawings.
   2. 3000 B.C., the Sumerians in Mesopotamia (what is today southern Iraq) devised cuniform
   3. Around 2000 B.C., Phoenicians created symbols
   4. The Greeks later adopted the Phoenician alphabet and added vowels; the Romans gave the letters Latin names to create the alphabet we use today.
2. Paper and Pens--input technologies.
   1. Sumerians' input technology was a stylus that could scratch marks in wet clay.
   2. About 2600 B.C., the Egyptians write on the papyrus plant
   3. around 100 A.D., the Chinese made paper from rags, on which modern-day papermaking is based.
3. Books and Libraries: Permanent Storage Devices.
   1. Religious leaders in Mesopotamia kept the earliest "books"
   2. The Egyptians kept scrolls
   3. Around 600 B.C., the Greeks began to fold sheets of papyrus vertically into leaves and bind them together.
4. The First Numbering Systems.
   1. Egyptian system:
      • The numbers 1-9 as vertical lines, the number 10 as a U or circle, the number 100 as a coiled rope, and the number 1,000 as a lotus blossom.
   2. The first numbering systems similar to those in use today were invented between 100 and 200 A.D. by Hindus in India who created a nine-digit numbering system.
   3. Around 875 A.D., the concept of zero was developed.
5. The First Calculators: The Abacus.
   
   One of the very first information processors.

B. The Mechanical Age: 1450 - 1840

1. The First Information Explosion.
   1. Johann Gutenberg (Mainz, Germany)
      • Invented the movable metal-type printing process in 1450.
   2. The development of book indexes and the widespread use of page numbers.
2. The first general purpose "computers"
   • Actually people who held the job title "computer: one who works with numbers."
3. Slide Rules, the Pascaline and Leibniz's Machine.
   • Slide Rule.
     Early 1600s, William Oughtred, an English clergyman, invented the slide rule
     • Early example of an analog computer.
   • The Pascaline. Invented by Blaise Pascal (1623-62).
     
     The Pascaline (front)
     
     (rear view)
     
     Diagram of interior
     
     • One of the first mechanical computing machines, around 1642.
   • Leibniz's Machine.Gottfried Wilhelm von Leibniz (1646-1716), German mathematician and philosopher.
     
     The Reckoner (reconstruction)
     
4. Babbage's Engines
   Charles Babbage (1792-1871), eccentric English mathematician
   
   
   • The Difference Engine.
     
     
     • Working model created in 1822.
     • The "method of differences".
   • The Analytical Engine.
     
     Joseph Marie Jacquard's loom.
     
     
     • Designed during the 1830s
     • Parts remarkably similar to modern-day computers.
       • The "store"
       • The "mill"
       • Punch cards.
     • Punch card idea picked up by Babbage from Joseph Marie Jacquard's (1752-1834) loom.
       • Introduced in 1801.
       • Binary logic
       • Fixed program that would operate in real time.
   • Augusta Ada Byron (1815-52).
     
   • The first programmer

C. The Electromechanical Age: 1840 - 1940.

The discovery of ways to harness electricity was the key advance made during this period. Knowledge and information could now be converted into electrical impulses.

1. The Beginnings of Telecommunication.
   
   1. Voltaic Battery.
      • Late 18th century.
   2. Telegraph.
      • Early 1800s.
   3. Morse Code.
      • Developed in1835 by Samuel Morse
      • Dots and dashes.
   4. Telephone and Radio.
      • 
        Alexander Graham Bell.
      • 1876
   5. Followed by the discovery that electrical waves travel through space and can produce an effect far from the point at which they originated.
   6. These two events led to the invention of the radio
      • Guglielmo Marconi
      • 1894
2. Electromechanical Computing
   1. Herman Hollerith and IBM.
      Herman Hollerith (1860-1929) in 1880.
      
      Census Machine.
      
      Early punch cards.
      
      Punch card workers.
      
      • By 1890
      • The International Business Machines Corporation (IBM).
        • Its first logo
          
   2. Mark 1.
      
      Paper tape stored data and program instructions.
      
      • Howard Aiken, a Ph.D. student at Harvard University
      • Built the Mark I
        • Completed January 1942
        • 8 feet tall, 51 feet long, 2 feet thick, weighed 5 tons, used about 750,000 parts

D. The Electronic Age: 1940 - Present.

1. First Tries.
   • Early 1940s
   • Electronic vacuum tubes.
2. Eckert and Mauchly.
   1. The First High-Speed, General-Purpose Computer Using Vacuum Tubes:
      Electronic Numerical Integrator and Computer (ENIAC)
      The ENIAC team (Feb 14, 1946). Left to right: J. Presper Eckert, Jr.; John Grist Brainerd; Sam Feltman; Herman H. Goldstine; John W. Mauchly; Harold Pender; Major General G. L. Barnes; Colonel Paul N. Gillon.
      
      
      Rear view (note vacuum tubes).
      
      • Electronic Numerical Integrator and Computer (ENIAC)
        • 1946.
        • Used vacuum tubes (not mechanical devices) to do its calculations.
          • Hence, first electronic computer.
        • Developers John Mauchly, a physicist, and J. Prosper Eckert, an electrical engineer
          • The Moore School of Electrical Engineering at the University of Pennsylvania
        • Funded by the U.S. Army.
        • But it could not store its programs (its set of instructions)
   2. The First Stored-Program Computer(s)
      
      The Manchester University Mark I (prototype).
      
      • Early 1940s, Mauchly and Eckert began to design the EDVAC - the Electronic Discreet Variable Computer.
      • John von Neumann's influential report in June 1945:
        • "The Report on the EDVAC"
      • British scientists used this report and outpaced the Americans.
        • Max Newman headed up the effort at Manchester University
          • Where the Manchester Mark I went into operation in June 1948--becoming the first stored-program computer.
        • Maurice Wilkes, a British scientist at Cambridge University, completed the EDSAC (Electronic Delay Storage Automatic Calculator) in 1949--two years before EDVAC was finished.
          • Thus, EDSAC became the first stored-program computer in general use (i.e., not a prototype).
   3. The First General-Purpose Computer for Commercial Use: Universal Automatic Computer (UNIVAC).
      
      UNIVAC publicity photo.
      
      • Late 1940s, Eckert and Mauchly began the development of a computer called UNIVAC (Universal Automatic Computer)
        • Remington Rand.
        • First UNIVAC delivered to Census Bureau in 1951.
      • But, a machine called LEO (Lyons Electronic Office) went into action a few months before UNIVAC and became the world's first commercial computer.
3. The Four Generations of Digital Computing.
   1. The First Generation (1951-1958).
      1. Vacuum tubes as their main logic elements.
      2. Punch cards to input and externally store data.
      3. Rotating magnetic drums for internal storage of data and programs
         • Programs written in
           • Machine language
           • Assembly language
             • Requires a compiler.
   2. The Second Generation (1959-1963).
      1. Vacuum tubes replaced by transistors as main logic element.
         • AT&T's Bell Laboratories, in the 1940s
         • Crystalline mineral materials called semiconductors could be used in the design of a device called a transistor
      2. Magnetic tape and disks began to replace punched cards as external storage devices.
      3. Magnetic cores (very small donut-shaped magnets that could be polarized in one of two directions to represent data) strung on wire within the computer became the primary internal storage technology.
         • High-level programming languages
           • E.g., FORTRAN and COBOL
   3. The Third Generation (1964-1979).
      
      
      1. Individual transistors were replaced by integrated circuits.
      2. Magnetic tape and disks completely replace punch cards as external storage devices.
      3. Magnetic core internal memories began to give way to a new form, metal oxide semiconductor (MOS) memory, which, like integrated circuits, used silicon-backed chips.
         • Operating systems
         • Advanced programming languages like BASIC developed.
           • Which is where Bill Gates and Microsoft got their start in 1975.
   4. The Fourth Generation (1979- Present).
      1. Large-scale and very large-scale integrated circuits (LSIs and VLSICs)
      2. Microprocessors that contained memory, logic, and control circuits (an entire CPU = Central Processing Unit) on a single chip.
         • Which allowed for home-use personal computers or PCs, like the Apple (II and Mac) and IBM PC.
           • Apple II released to public in 1977, by Stephen Wozniak and Steven Jobs.
             • Initially sold for $1,195 (without a monitor); had 16k RAM.
           • First Apple Mac released in 1984.
           • IBM PC introduced in 1981.
             • Debuts with MS-DOS (Microsoft Disk Operating System)
         • Fourth generation language software products
           • E.g., Visicalc, Lotus 1-2-3, dBase, Microsoft Word, and many others.
           • Graphical User Interfaces (GUI) for PCs arrive in early 1980s
             • 
               MS Windows debuts in 1983, but is quite a clunker.
               
               • Windows wouldn't take off until version 3 was released in 1990...