C Programming Tutorial. Previous: (dir). Up: (dir)C Programming Tutorial (K& R version 4)This is a C Programming Tutorial for people who have a little experience. Emacs Lisp or a GNU shell.
C program to check a string is palindrome or not using strrev function and without using string library functions with Sample Input and Output. Differences Between Formal Arguments and Actual Arguments of a Function; Explain command line arguments of main function; What is the purpose of main.
Unlike BASIC or Pascal, C was not written as. C is a computer. language and a programming tool which has grown popular because. It is a tricky language but a masterful. Sceptics have said that it is a language in which everything which. True, it does not do much hand holding, but.
If you have come to C in the hope. C is ideally suited to modern. Its aim is to teach C to a beginner, but with. When it comes down to it, most languages have basically.
If you want to plan. C, think about what you already know about programming. C. You will most likely find all of. In places. these examples make use of features before they have properly been. These programs serve as a taster of what is to come.
This book was first written in 1. Traditionally this is an executable. C Compiler. gcc filename. On GNU systems, this results in the creation of an executable. To tell the compiler. For example, to create a program called myprog from a file.
Next: Use of Upper and Lower Case. Previous: The compiler. Up: Introduction. Errors. Errors are mistakes which we the programmers make. The situation thus looks much worse than it really is.
You'll. get used to this with experience, but it can be very disheartening. This is a potential source of quite trivial. If you. use a word which has already been adopted in a library, there will be a. How is it created? The basic control of a computer rests with its operating system. This is. a layer of software which drives the hardware and provides users with a. An operating system has two.
The operating. system is the route to all input and output, whether it be to a screen. A programming language has to get at this input. In C the link between these two is very efficient. GUIs are good for carrying out.
For that one needs a command. In the network version of this book we shall concentrate on. Unix shell commands since they are the most important to programmers. Many compiler languages still have this inadequacy when. C is an exception, because of its.
Input and output are not actually defined as a fixed. C language. Instead there is a standard file. This file is called a standard C library. In many operating. C does this implicitly (it comes from Unix).
The file. from which C normally gets its input from is called stdin or. The corresponding. Both of these are parts of stdio or. The keyboard and the monitor screen are.
The advantage of treating devices like this is that it is not. In other words, it is exactly the same to read or write from a. This is a great. simplification of input/output! The filenames of devices (often given. For instance, the printer might be called . You might have to open it explicitly as a file.
The compiler generates a file of object code from. The final program. Unix- like. operating systems, and filename. EXE on Windows derived.
The libraries themselves are also files of object code, typically. The dotted endings mean that the. The quad file and the object. The . c suffix is to tell the compiler that. C source program and similarly the other letters. This means. the instructions which can be given to the system itself rather than the.
C program. Fortunately it. Every. system will have its own way of halting or terminating the operation of. Commonly this will involve two.
CTRL C, CTRL Z or. CTRL- D etc. In GNU/Linux, CTRL- C is used. Header files. The core of the C language is small and simple. Special functionality.
Some libraries are provided for you, giving. We shall return to this later. Each library comes with a number of.
It. is up to every programmer to make sure that libraries are added at. For. example, to merge with the math library libm. If we wanted to add in the socket. When library functions are used in.
You cannot then use the names of functions or macros. This belongs to a subset of the standard. C library which deals with file handling.
The math. h header file. For instance. #include < stdio. These details will be. C compiler or operating. Libraries also add to the time it takes to compile a. Some operating systems are smarter than others when running. Others have to load in everything before they can run a.
Unix users are lucky in having an online. This means that there are.
This has both advantages and dangers. The. advantage is that the user is free to choose a style which best suits. The disadvantage is that, unless a strict style is. The reasons for. choosing a well structured style are that. Long programs are manageable only if programs are.
Such a scheme becomes. In the end, experience and good judgement are the factors. The. main goal of any style is to achieve clarity. All computers today are equipped with more than enough memory. What will it look like? C is made up entirely of building blocks which have a particular `shape'. The form is the same everywhere in a program, whether it is the.
A program is made up of. Every C. program is a collection of one or more functions, written in some. One and only one of these functions in the program must.
This function is always the starting point of a C. C program would be just a single function. This is how C distinguishes functions from ordinary variables. It always starts. Only the operating system can call. C program is started. There are several new things to notice about this.
Firstly the function do. This is all that is required to transfer control to the new. In some languages, words like CALL or PROC are used, or even.
No such thing is needed in C. All instructions in C must end with a. This is a signal to inform the compiler that the end of a. This helps the compiler diagnose errors. This is the simplest way. C. The function main(). When a program is compiled, each.
Here are some more basic elements. The following. chapters will then expand upon this as a kind of basic plan. What does this. character signify? Programs can. contain any number of comments without losing speed.
This is because. comments are stripped out of a source program by the compiler when it. You should try to minimize the use of comments in. That is if the programmer.
Getting results. A function is a module or block of program code which deals with a. Making functions is a way of isolating one block of. They allow a programmer to say: `this piece of code does a.
A function can accept a number of parameters or values. The declarations and `type of. The name of a function must begin with an alphabetic letter. Z(any letter from A to Z). All the variables are chosen to be integers to keep things. The details are quickly. It has to be called.
A function is called. Here is a simple program which makes. The structure diagram shows. The idea is to illustrate the way in which the functions connect. Next: Program listing.
Previous: Functions. Up: Functions. Structure diagram. Level 0: main (). Some functions. call themselves, while others can be called from anywhere in a program.
In. C it is possible to choose whether or not a function will have a. It is possible to make a function hand back a value to the.
Take the following example. Calculate. Bill(data..). The variable bill is assigned to a function. Calculate. Bill() and data are some data which are passed to. This statement makes it look as though. Calculate. Bill() is a number.
When this statement is executed in a. Calculate. Bill(). The. value of the function is assigned to . If there were. no return statement the program could not know which value it should. Calculate. Bill and so it would not be. Forgetting a. return statement can ruin a program. For instance if Calculate.
Bill. Calculate. Bill (starter,main,dessert) /* WRONG! On the. other hand if the first version were used (the one which did use the. This is usually what is done with the input output. So a function in C can return a value but it does not have to be. This is where the beauty of the return statement becomes. The program can simply call return(value) anywhere in the.
The function is entered with some values for. C's loops called while. In that loop. is a single if statement and a statement which increases a by one. If a becomes bigger than b at any point the. This is called with a return code, like this.
CODE 0. This function also calls a number of other functions which perform. But what happens if a function is required to return a. A statement like. Calculate. Bill (a,b,c). Calculate. Bill() are the same kind of object: in other.
Calculat. Bill() returns a floating point number, then. Both sides of an assignment must. So far no declarations have been needed because C assumes that.
Declarations are covered in the next section. Declaring data. A variable is a seqeuence of program code with a name (also called its. The name of a variable must begin with an. Z(any letter from A to Z). In BASIC and in some older, largely obsolete. PL/1, a special naming convention is used to determine.
No. such convention exists in C. Instead we specify the types. This serves two purposes. It gives a compiler precise information about the. In fact it is possible. C ready for use. The names of these types are all reserved.
C and they are summarized as follows. A single ASCII character. A short integer (usually 1. A short integer. int A standard integer (usually 3.
A long integer. long int A long integer (usually 3. A floating point or real number (short). A long floating point number.
Discussed in a later chapter. In. addition to the above, the word unsigned can also be placed in.
Unsigned means that only positive or zero. The advantage of.
The ANSI standard also. On some systems variables are signed. A compiler is. markedly more efficient than a customs officer: it will catch a. For now it will do to simply state. That is, in. the space between function definitions. Another name for them is automatic variables. This is no more efficient than doing it in.
The following. are equivalent to the more longwinded. This is called initialization of the variables. C always allows. the programmer to write declarations/initializers in this way, but it is.