Page 10 - DCAP407_DATA_STRUCTURE

Unit 1: Introduction to Data Structures

Instructions for assembling a puzzle can be an example of an algorithm. If you
are given a preliminary set of marked pieces, you can follow the instructions
given to complete the puzzle.
According to Levitin, algorithms can be defined as, “A sequence of unambiguous instructions for
solving a problem, i.e., for obtaining a required output for any legitimate input in a finite amount of
time.”
Most computer programs involve an algorithm and one or more data structures. An appropriate data
structure needs to be selected for an algorithm as the efficiency of the algorithm depends on the data
structure chosen. By increasing the data storage space, you may not be able to reduce the time needed
for processing the data and vice versa.

When we want to print a mailing list alphabetically we need to use a data
structure and an algorithm. We first arrange all the names in a data structure
(array) and then sort the names alphabetically using an algorithm (sorting).
1.1.2 The Concept of Data Type
A data type comprises a set of data with values and consists of predefined set of characteristics. To be
specific, data is usually stored in a variable, where the value of the variable changes according to the
program being executed. The four commonly used data types in C language include int (integer), float
(real number), char (character) and pointer. The keywords int, float, char and so on always take
lowercase letters. Generally, a data type includes constants and variables. A constant is considered as an
entity that does not change in any given program. A variable is an entity that may change from one
program to another. It is necessary to specify the variables that will be used in a program. Therefore,
type declaration is made by giving the data type and then the variable names. The syntax for declaring
the data type and the variable name is as given below:
Syntax:

<(data type)><variable names>;

int x;
Where, int is a data type and x is a variable
Integer Data Type
An integer data type includes only whole numbers. It does not contain any fractional data. It is denoted
by the keyword int. It occupies 2 bytes of memory space. Integer data type can either be signed or
unsigned. The signed type integer takes both positive and negative values. The range of integer
constant is from -32768 to +32767 (-2^15 to +2^15 - 1) for a 16-bit compiler and -128 to 127 (-2^7 to +2^7
- 1) for an 8-bit complier. A 16-bit compiler uses one bit for storing sign and the remaining 15-bits for
storing numbers. An 8-bit complier uses one bit for storing sign and the remaining 7-bits for storing
numbers. The unsigned integer ranges from 0 to 65535. The signed and unsigned integers are specified
as follows:
Syntax:
Unsigned int value;
Signed int value;
The integer data type is denoted by placeholder format string % d, which indicates that the data being
used is of integer values.

int x;
scanf (“%d”, &x);

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