by Dinesh Thakur

If you construct a long program today and try to recall it after a few days, there is every possibility that you would have forgotten quite a few things and even what the program does or what a particular name stands for. Comments if included in a program help in recollection of different names, data values and other parameters.

 
by Dinesh Thakur

Escape sequences are basically control characters used for formatting the output. These are combinations of a backslash and a character in lowercase. We have already used "\n", which shifts the curser to the next line. Table lists the escape sequences defined in C language.

 
by Dinesh Thakur

(i) It is a structured high-level language and is highly portable to different platforms.

(ii) C is closest to assembly language and hence it is extremely efficient. Some programmers call it "high-level assembly language", although it is not a justified comment.

 
by Dinesh Thakur

We can read a string using the %s conversion specification in the scanf function. However, it has a limitation that the strings entered cannot contain spaces and tabs. To overcome this problem, the C standard library provides the gets function. It allows us to read a line of characters (including spaces and tabs) until the newline character is entered, i. e., the Enter key is pressed. A call to this function takes the following form:

 
by Dinesh Thakur

The standard C library provides several functions and macros for character 1/0. Here we consider the getchar and putchar macros. As these macros read or write a single character, they are typically used in a loop to read/write a sequence of characters.

 
by Dinesh Thakur

The C standard library provides the executable code and declarations for functionality provided in it. The executable code for the library is provided in separate files, usually in the lib directory, in the installation directory of the compiler. The library files in Turbo C/C++ are named *.LIB, whereas those in the MinGW compiler provided with Dev-C++ and Code :: Blocks are named lib*. a.

 
by Dinesh Thakur

BASIC stands for beginner's all-purpose symbolic instruction code, and is a computer programming language that was invented in 1964 at Dartmouth University by John G Kemeny and Thomas E Kurtz. BASIC has the advantage of English-like commands that are easier to understand and remember than those of most other languages. Even so, the latest versions of BASIC can do just about anything programming languages like C or Pascal can do.



 
by Dinesh Thakur

ANSI C: The current standard version of the C language, subject of ANSI standard X3.4-1968. It added several important features tothe language, including function prototypes,STRUCTURE passing and structureASSIGNMENT.

 
by Dinesh Thakur

Gets() perform on strings of characters. The function gets (Name_of_string) reads characters from an input stream into the arraypointed to by Name_of_string until it encounters EOF or end-of-line character, which is discarded and null character is substituted instead.

 
by Dinesh Thakur

The function printf () is used for displaying the output of a program on the monitor, while the function scanf () is used for providing input to the program from keyboard. We shall first discuss printf(). If only a text statement is to be displayed on the monitor as was done in Program, then the argument of the function printf() is the string enclosed in double quotes (" " ) as illustrated below.

 
by Dinesh Thakur

The function getchar () reads a single character at a time, i.e., it gives access to a single character which may be manipulated. For instance, the character may be changed by a new character, a lowercase letter may be changed to an upper case letter or vice versa, or a character may be removed from the string, and so on. However, for reading the complete string you have to use a loop.

 
by Dinesh Thakur

The modifier const causes the variable can not be changed in the program. As the name suggests it is useful to declare constants. We could have, for example:

 
by Dinesh Thakur

The anatomy of a program

We have some compiler preprocessor commands. This includes various #include files. Then comes the main function. Some name can also be given to the main function. Then, we have the variable declarations used in the main code. Then we have sub-functions.

 
by Dinesh Thakur

There are many "languages" like, for example C, Fortran, PASCAL etc., that help us to convert an algorithm in to something that a computer can understand. We will focus here only on C programming So. let us start looking at how do we create a "C program".



 
by Dinesh Thakur

Martin Richards developed a high-level computer language called BCPL in the year 1967. The intention was to develop a language for writing an operating system (OS). As you know an OS is software which controls the various processes in a computer system. This language was later improved by Ken Thompson and he gave it a new name B. The basic ideas about some topics such as arrays, etc., which were later inherited by C were developed in BCPL and B. In those days, the development of computers was in infancy. One of the serious constraints experienced while developing the language B was the small computer memory available at that time.



 
by Dinesh Thakur

Another component common to C programs is the header file. This supplies information about the standard library functions. These files all end with the .h extension and are added to the program using the #include pre-processor directive. All C compilers use a pre-processor as their first phase of compilation to manipulate the code of the source file before it is compiled.



 
by Dinesh Thakur

The main role of header file is it is used to share information among various files.To put it brief, if we have several functions say 4 functions named as f1, f2, f3, f4 placed in file say sample.c and if all the functions want to get accessed each other all must be placed in the same file sample.c. 



 
by Dinesh Thakur

when we said that every language consists of keywords and that these keywords are only understandable by the people who speak the language.The same is with C; keywords are special words that have special meaning in the C language and are reserved by the language. That last sentence has significant meaning, so I will take about it a little later on.