Skip to main content

Explain the Identifiers, Keywords and Tokens

 .

Tokens

A token is the smallest unit used in a C program. Token can define in C as the smallest individual elements in a program that is meaningful to the functioning of a compiler.
The following are the types of tokens: Keywords, Identifiers, Constant, Strings, Operators, etc.

Identifier

Identifier refer to the name of user define variable, array and function. A identifier should be essentially  a sequence of latter and digits. It is a type of string of alphanumeric characters that always begins with either an alphabetic or underscore character. There are specific rules to define the identifiers, and we can not use the already defined keywords present in the C language as identifiers.

 Valid Identifier

 Invalid Identifier
sum12 

12sum 

 Temp

goto 

 emp_12

emp12 

Internal identifier

Internal identifiers are the ones that are not used in any of the external link processes. Internal identifiers, also known as internal names, include the names of local variables. The internal identifier can be a local variable. It has at least 31 significant characters.

External identifier

External identifiers are the ones that are used in an external link process. These identifiers are also known as external names; include function names and global variable names that are shared between source files. The external identifier can be a name of function or a global variable. It has at least 63 significant characters.


Keywords 

Keywords are predefined, reserved words used in programming that have special meaning to the compiler. Keywords are part of the syntax and part of the syntax and they cannot be used as an identifier. These are the reserved words having predefine meaning in c program. These are 32 keywords as following.

 Auto

 double 

int 

struct 

break 

 else

long 

 switch

case 

enum 

register 

typedef 

char 

extern 

return 

 union

continue 

for 

signed 

void 

default  

goto 

sizeof 

volatile 

constant 

 float

short 

unsigned 




Comments

Post a Comment

Popular posts from this blog

Introduction of Computer

.  A computer is an electronic device. It take input and store the data in memory and performing the function to produce accurate result in output device. It is used to type document, send email, play game, browse the web and entertainment.   Characteristics of computer  1 . High speed  Computer is very fast device. It is capable of performing calculation of very large amount of data. The computer has unit of speed in microsecond, nanosecond and even in picosecond. The computer is capable of performing millions of tasks per second. 2. Accuracy  The computer produces highly accurate and reliable result.  It does not make any kind of mistake in calculating. The calculation are 100% error free. The computers perform accurate 'n' number of times. 3. Storage capability A computer has much more storage capability. It can store large amount of data. It can store any type of data such as image, video, text document, audio and many more. 4. Diligence Diligence ...
1 comment
Read more

Introduce Linux, UNIX and Linux distribution.

 . Linux Linux is an open source operating system. The term Linux is actually referred to mean a kernel of Unix like operating system developed by a Finish software architect Linus Torvald. The name Linux is derived from Linus' Unix. Linux was originated from the inspiration of a small Unix like operating system MINIX by A.S Tanenbum. Linux is a complete multiuser, multiprocessing, secure and stable operating system which is also considered as UNIX clone. However no code from the proprietary from AT and T is included in Unix. It has flavor of Unix but is not Unix. UNIX  UNIX is a layered operating system. The innermost layer is the hardware that provides the service for the OS. The operating system, referred to in UNIX as the kernel, interacts directly with the hardware and provides the services to the user program. These user programs don't need to know anything about the hardware. They just need to know how to interact with the kernel and it's up to the kernel to provide ...
Post a Comment
Read more

Open System Interconnect (OSI) Reference Model

 . Open system interconnection (OSI) Model explains how packet travels through various layers to other devices on a network, even if the sender and destination have different types of network media. Layer 1(Physical layer):  Function  To activate, maintain, deactivate the physical connection.  To define voltage and data rates needed for transmission.  To convert the digital bits into electrical signals.  To decide weather the transmission the transmission is simplex, half or full duplex.  Physical layer doesn’t perform the detection and correction of errors. Layer 2 (Datalink layer):  Framing (stream of bits into manageable data units):  The datalink layer divides the stream of bits received from the network layer into frame manageable data units called frames.  Physical addressing (MAC Address):  Data link layer adds a header to header to the frame to define the sender and receiver of the frame. Flow Control (mechanism for overwhel...
Post a Comment
Read more