Problem Solving and Computer Programming Using C

Contents

Preface

Acknowledgement

The first step in writing instructions to carry out a task is to determine what the output should be, that is, exactly what the task should produce. The second step is to identify the data, or input necessary to obtain the output. The last step is to determine how to process the input to obtain the desired output. We determine what we want, get the needed input and process the input to produce the desired output.

C is a general purpose, structured programming language. C was developed and first implemented by Dennis Ritchie at Bell Laboratories in the 1970’s. Since it was developed along with the Unix Operating system, it is strongly associated with Unix. This operating system, which was also developed at Bell Laboratories, is coded almost entirely in C. C is often called a middle level computer language. It is because it combines the best elements of high level languages with the control and flexibility of assembly language. C code is portable. Portability means that it is easy to adapt software written for one type of computer operating system to another type.

Variable is an identifier that is used to represent some specified type of information within a designated portion of the program. It is named location in memory that is used to hold a value that can be modified by the program. All variables must be declared before they can be used. Variables can be declared at the start of any block of code, but most are found at the start of each function.

The C language is accompanied by a number of library functions. These library functions are not part of the language, though all implementations of the language include them. Some functions return a data item to their access point; others indicate whether a condition is true or false.

Many modern computer programs are designed to create an interactive dialog between the computer and the person using the program. These dialogs usually involve some form of question—answer interaction, where the computer asks the questions and the user provides the answers, or vice versa.

A program is made up of one or more functions, with one of these being main(). Function is a self-contained block of program that performs a particular task.

Every variable and function in C has two attributes: type and storage class. If we don’t specify the storage class of a variable in its declaration, the compiler will assume a storage class dependent on the context in which the variable is used. C has got certain default storage classes.

Many applications require the processing of multiple data items that have common characteristics. In such situations it is often convenient to place data items into an array, where they will all share the same name(e.g., arr). The individual data items can be characters, integers, floating-point numbers, etc. However, they must all be of the same type and the same storage class.

Array is a data structure whose elements are all of the same data type. The structure is a data structure whose individual elements can differ in type. Thus, a single structure might contain integer elements, floating-point elements and character elements. Pointers, arrays and other structures can also be included as elements within a structure. The individual structure elements are referred to as members. We will see how structures are defined, and how their individual members are accessed and processed within a program.

A simple variable in a program is stored in a certain number of bytes at a particular memory location, or address, in the machine. Pointers are used in programs to access memory and manipulate addresses.

Many applications require that information be written to or read from an auxiliary memory device. Such information is stored on the memory device in the form of a data file. Thus, data files allow us to store information permanently, and to access and alter that information, whenever necessary. In C, an extensive set of library functions is available for creating and processing data files.

There is only one programming language that any computer can actually understand and execute: its own native binary machine code. This is the lowest possible level of language in which it is possible to write a computer program. All other languages are said to be high level or low level according to how closely they can be said to resemble machine code.

University Questions

Index