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Basic syntax of C programming

What is C syntax like? How are identifiers in C? Let's find out with Quantrimang.com!

Tokens in C

The C language includes many different tokens and a token can be a keyword, an identifier, a constant, a string or a character. For example, the C command line below includes the following 5 tokens:

printf("Hello, World! \n");

The individual tokens are as follows:

printf
(
"Hello, World! \n"
)
;

Semicolon ; in C

C program, semicolon is part of the end of the command. In fact, every command in C must end with a semicolon. It announces the end of a logical attribute.

For example, below are 2 commands:

printf("Hello, World! \n");
return 0;

Comments in C

Comments are like help in C programs and are ignored by the compiler. It starts with /* and ends with the character */ as shown below:

/* Day la chuong trinh C dau tien */

You cannot have an additional comment section inside this comment section.

Identifier in C

An identifier in C is a name used as a variable, function, and user-defined element. An identifier can begin with the characters A to Z, a to z and an underscore (_) and the numbers 0 to 9.

C does not allow signs such as @, $, and % in identifier names. C is a differentiated language lower case – upper case. Therefore, QTM and qtm are two different identifiers in C. Here are a few valid identifier examples:

nam       hoangminh    abc   ha_noi  a_123
sinhvien   _hocphi  j     d23b5      nhanVien

Keywords in C

Below is a list of reserved keywords in the C language. Identifiers, variables, and constants cannot be named the same as the keywords below, otherwise the program will report an error.

auto else. else long. long switch. switch
break. break enum register typedef
case. case extern return union. union
char float. float short unsigned
const for signed void. void
continue goto sizeof volatile
default if static. static while
due int struct _Packed
double

Whitespace in C

A line may contain whitespace, which may be comment lines, known as blank lines as they are ignored by the compiler when compiling.

A space in C can be a blank paragraph, tab, newline (new line) or comment. A space divides one part of a command into multiple parts and helps the compiler distinguish between one element in a command, such as int, the end of one element, and the beginning of the next element as in the following command:

int diemthi;

There must be at least one space character between int and diemthi for the compiler to understand and distinguish between them. Otherwise, see the command below:

luong = luongcoban + phucap;   // tinh tong luong

There is no need for a space between luong and the = sign, or between the = sign and luongcoban.

Example of basic C syntax

#include 

int main() {
  printf("Chào mừng tới Quantrimang.com!");
  return 0;
}

Detailed explanation

Line 1: #include is a header file library, allowing programmers to work with input and output functions, such as printf() (used in line 4). File Header adds functionality to C programs.

Don't worry if you don't understand how #include work. Just think that it is an ingredient that often appears in the program.

Line 2: A blank line C ignores whitespace. However, for example, use it to make the code easier to read.

Line 3: Another element, always present in C programs is main(). It is called a function. Any code inside curly braces will be deployed.

Line 4: printf() is a function used to output/print text on the screen. In the above example, “Welcome to Quantrimang.com” will appear or be output.

Note:

  • Every command in C ends with a semicolon.
  • The body part of C is also rewritten as: int main(){printf("Chào Quantrimang.com!");return 0;}
  • Remember that the compiler ignores whitespace. However, more lines make the code easier to read.

Line 5: return ) end main() function.

Line 6: Don't forget to add a closing curly brace to end the function main.

C syntax

Previous lesson: Basic C program structure

Next lesson: Data types in C programming

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