This presentation explains following points of C language briefly - 1. KEYWORDS 2. IDENTIFIERS 3. CONSTANTS 4. STRINGS 5. SPECIAL SYMBOLS 6. OPERATORS ------------------------------------------------------------------------------------------------------------ YOUTUBE CHANNEL - https://www.youtube.com/c/NAVEENSHARMAsCLASSROOM ----------------------------------------------------------------------------------------------------------- TELEGRAM CHANNEL - https://t.me/BCA_FIRST_YEAR ----------------------------------------------------------------------------------------------------------------- FACEBOOK PAGE - https://www.facebook.com/Naveensharmasclassroom-105183924735146 ---------------------------------------------------------------------------------------------------------

1. Fundamentals of C
C TOKENS
• Tokens are the smallest individual units of a c program. There are six types of tokens in c language as shown in
following figure :-

2. Fundamentals of C
KEYWORDS AND IDENTIFIERS
• Every C word is defined as either keyword or an identifier.
• A keyword is a word or phrase which has fixed meaning and its meaning cannot be changed.
• Keywords serve as basic building blocks for program statement. The list of C keywords are listed in below Table :-
Table – C Keywords

3. Fundamentals of C
KEYWORDS AND IDENTIFIERS
• Identifiers refers to the name of variables, functions and arrays.
• These are user-defined names and consist of a sequence of letters and digits, with a letter as a first character.
• Both uppercase and lowercase letters are permitted; lowercase letters are used very frequently.
• Underscore character is used as identifier also and it used as link to connect two words in long identifiers.
• There are following rules to define an identifier :-
1. First character must be an alphabet ( or underscore ).
2. An identifier must consist of only letters, digits or underscore.
3. Only first 31 characters are considered significant.
4. An identifier must not contain white space.

4. Fundamentals of C
CONSTANTS
• Constants in C language refers to fixed values that do not change during the execution of a program.
• C language has several types of constants as shown in following figure :-
CONSTANTS
NUMERIC
CONSTANTS
CHARACTER
CONSTANTS
INTEGER
CONSTANTS
REAL
CONSTANTS
SINGLE CHARACTER
CONSTANTS
STRING
CONSTANTS
Fig : Basic Types of C constants

5. Fundamentals of C
CONSTANTS
• Integer Constants -
1. Integer constants refer to a sequence of digits.
2. There are following three types of integers :-
I. Decimal Integers -
• Decimal integer consists of a set of digits , 0 through 9, preceded by an optional – or + sign.
• Examples :- 123 -321 0 654321 +78
• Embedded spaces, commas, and non-digit characters are not permitted between digits .
For example, 18 750 20,000 $1000 are illegal numbers.
II. Octal Integers –
• An octal integer constant consists of any combination of digits from the set 0 through 7, with a
leading 0. Some examples of octal integer are : 037 0 0435 0551
III. Hexadecimal Integers –
• A sequence of digits preceded by 0x or 0X is considered as hexadecimal integers.
• They may also include alphabets A through F or a through f , the letter A through F represent the
numbers 10 through 15.
• Examples :– 0X2 0x9F 0Xbcd 0x

6. Fundamentals of C
CONSTANTS
• Real Constants –
1. Integer numbers are not sufficient to represent quantities that vary continuously, such as distances, heights,
temperatures, prices, and so on.
2. These quantities are represented by numbers containing fractional parts like 17.584.
3. Such numbers are called real ( or floating point ) constants.
4. Examples :- 0.0083 -0.75 435.36 +84.0 0.65e4 12E-2
5. Real Constants can be expressed in following two types of notations :-
I. Decimal Notation :- 215.15 210. -.71 +.5 +85.0 -112.5
II. Exponential ( Scientific ) Notation :-
• mantissa e exponent
• 0.5e4 18e-2 1.5e+5 3.18E3 -1.2E-1
• This notation is useful to represent which are very large or small in magnitude. For example,
85000000000 can be written as 8.5E10 or 85E9
• Similarly 0.000000036 is equivalent to -3.6E8
6. These constants are normally represented as double-precision quantities . Suffix f or F is used to force single
digit precision and l or L is used to force double digit precision further.

7. Fundamentals of C
CONSTANTS
• Single Character Constants –
1. A single character constant (or simply character constant) contains a single character enclosed within a pair of
single quote marks.
2. Example:- ‘5’ ‘a’ ‘A’ ‘;’ ‘ ‘
• String Constants –
1. A string constant is a sequence of characters enclosed in double quotes. The characters may be letters,
numbers, special characters and blank space.
2. Example :- “Hello!” “2020” “GOOD MORNING” “?.......!” “5+3” “X”

8. Fundamentals of C
VARIABLES
• A variable is nothing but a name given to a storage area that our programs can manipulate.
• Unlike constants that remain unchanged during execution of program, a variable may take different values at different
times during execution of program.
• Each variable in C has a specific type, which determines the size and layout of the variable's memory; the range of
values that can be stored within that memory; and the set of operations that can be applied to the variable.
• A variable name may consist of letters, digits, and the underscore(_)character, subject to the following conditions :-
1. They must begin with a letter. Some systems permits underscore as the first character.
2. Standard length for a variable name is 31 characters. However length should not be more than eight characters,
since only first 8 characters are treated as significant by many compilers.
3. Uppercase and lowercase are significant i.e. the variable Total is not same as total or TOTAL.
4. It should not be a keyword.
5. White space is also not allowed
• A variable name can be chosen by the programmer in a meaningful way so as to reflect its function or nature in the
program. Example :- Average, height, Total, Counter_1, class_strength, distance, ph_value, mark.
• Some Invalid examples of variables are 123 (area) % 25th

9. Fundamentals of C
DATA TYPES
• Data types refers to an extensive system used for declaring variables or functions of different types.
• Data types specify how we enter data into our programs and what type of data we enter.
• The type of a variable determines how much space it occupies in storage and how the bit pattern stored is
interpreted. This determines the type and size of data associated with variables.
• Each data type requires different amounts of memory and has some specific operations which can be performed over
it.
• There are three classes(types) of data types :
1. Primary (or fundamental) data types
2. Derived data types
3. User-defined data types

10. Fundamentals of C
DATA TYPES
1. Primary (or fundamental) data types –
• Every C compiler supports following types of primary data types :
Fig : Primary data types in C
l

11. Fundamentals of C
DATA TYPES
1. Primary (or fundamental) data types –
I. Integer Types –
• Integers are whole numbers with a range value supported by a particular machine.
• Integers are defined in C by the keyword int.
• Generally integers occupy one word of storage, and since the word sizes of machines vary (typically 16 ,32 or 64 bits) the
size of an integer that can be stored depends on the computer.
• If 16 bit word length is used , the size of the integer value is limited to the range -32768 to +32767(that is,
−215
𝑡𝑜 +215
−1.
• For 32 bit machine the range id -2,147,483,648 to 2,147,483,647.
• A signed integer uses one bit for sign and 15 bits for the magnitude of the number .
• C language has 3 classes of integer storage, namely short int, int, and long int, in both signed and unsigned forms.
Unlike signed integers , unsigned integers use all the bits for magnitude of the number and are always positive.
• We use long and unsigned integers to increase the range of values.

12. Fundamentals of C
DATA TYPES
1. Primary (or fundamental) data types –
II. Floating Point Types –
• Floating point numbers are stored in 32 bits ( on all 16 bits and 32 bits machines), with 6 digits
precision.
• Floating point numbers are defined in C by the keyword float.
• When the accuracy provided by a float number is not sufficient, the type double can be used to
define the number.
• A double data type number uses 64 bits giving a precision of 14 digits. These are known as
double precision numbers.
• To extend the precision further, we may use long double which uses 80 bits.
float
double
long double

13. Fundamentals of C
DATA TYPES
1. Primary (or fundamental) data types –
III. Character Types –
• A single character can be defined as a character(char) type data.
• Characters are usually stored in 8 bits (one byte) of internal storage.
• The qualifier signed or unsigned may be explicitly applied to char.
• While unsigned chars have values between 0 and 255, signed chars have values from -128 to 127.
IV. Void Types –
• The void type has no values.
• This is usually used to specify the type of functions. The type of a function is said to be void when it does
not return any value to the calling function .

14. Fundamentals of C
DATA TYPES
1. Primary (or fundamental) data types –
Table : Size and Range of Data Types on 16-bit machine

15. Fundamentals of C
DATA TYPES
2. Derived data types –
• C supports three derived data types :-

16. Fundamentals of C
DATA TYPES
3. User-defined data types –
• C supports the feature called type definition which allows the programmer to define their identifier that would
represent an existing data types. There are three such data types: