Data Structures, Strings, and Pointers in C

Posted on Mar 3, 2025 in Computers

What is a Parent?

It’s a way of handling a large amount of data of the same type under one name or identifier.

Arrays: State and Data Access

Arrays are declared in a similar way, with separate brackets for each subscript. The general form of the declaration is:

type name [row_num] [num_columns];

The way to access the array elements is by using its name followed by the integer expressions for the two subscripts in square brackets.

What is a String?

A string is simply a vector of type char. It is declared in the following form:

type name [positions]

The special characteristic is that they usually contain text strings, and this is stored in the initial part of the chain.

Special Functions for String Treatment

  • strlen(): The prototype of this function is as follows:
    • unsigned strlen(const char *s);
    • Its name comes from string length, and its mission is to count the number of characters in a string, not including the '\0' end.
  • strcat() Function:
    • The prototype of this function is:
    • char *strcat(char *s1, const char *s2);
    • Its name comes from string concatenation and is used to concatenate two strings: s1 followed by s2.
  • strcmp() Function:
    • The prototype of this function is:
    • int strcmp(const char *s1, const char *s2);
    • Its name comes from string comparison and compares two strings.
    • The strcomp() function is completely analogous, except that it is case-insensitive.
  • strcpy():
    • The prototype of this function is:
    • char *strcpy(char *s1, const char *s2);
    • Its name comes from string copy and serves to copy strings.

Difference Between scanf/printf and gets/puts

The printf() function prints the output in the text, variables, and constants that are indicated.

printf("control_string");

While scanf(), in many respects, is analogous to printf() and is used to read data from standard input (keyboard). The general form of this function is the following:

scanf("%such thing", &argument);

The gets() function is used to read strings:

char sentence[100];
printf("Enter a sentence");
gets(sentence);

While the puts() function is used to print strings:

What is a Data Structure?

A data structure is a way to group a set of data of various types under the same name or identifier. It is declared as follows:

struct student {
  char name[31];
  char address[30];
  char phone[30];
};

To access the members of a structure, write the name of the structure, then a dot (.), followed by the name of the member. Example:

student.phone = 54546;

Data are assigned in the following form:

struct student new_student_class[300];

What is a Function?

Functions are subroutines of a program divided to make it more manageable and smaller. They are used to divide programs into subprograms that are called by the main program.

What is a Pointer?

A pointer is a variable that can contain the address of another variable. It must be declared or defined according to the type of data pointed to.

Declaration: int *address;

What is a File?

A file is any code for any program written in C, which is stored on a computer disk.

File Types

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File Variable Declaration

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Data Access and Storage

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Considerations When Working with Files

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