C Programming Chapters 7-10

A pointer is a variable that stores the memory address of another variable.

Arithmetic operations like addition, subtraction, multiplication, and division are generally not valid on pointers. It is because pointers store memory addresses, and performing mathematical operations on addresses can lead to unpredictable results and memory corruption.

An array of pointers is an array where each element of the array holds pointers to other variables. For example, an array holding pointers to integers could store the memory addresses of multiple integer variables.

<p>A pointer to pointer, also called double pointer, is a variable that holds the memory location of another pointer. For example, a pointer to a pointer can point to the address of another pointer which is holding the address of an integer variable.</p> Signup and view all the answers

<p>A structure variable is a collection of different data types grouped together under a single name. A pointer to structure variable, on the other hand, holds the memory address of a structure variable, allowing for efficient access and manipulation of its members.</p> Signup and view all the answers

<pre><code class="language-c">struct time_struct { int hours; int minutes; int seconds; }; int main() { struct time_struct time_data; time_data.hours = 10; time_data.minutes = 30; time_data.seconds = 15; printf(&quot;Time: %02d:%02d:%02d\n&quot;, time_data.hours, time_data.minutes, time_data.seconds); return 0; } </code></pre> Signup and view all the answers

<p>A structure is a user-defined data type that groups together related variables of different data types. The members of a structure can be accessed using the dot operator (.) or arrow operator (-&gt;). The size of a structure is the total amount of memory required for storing all its members, which can be determined using the <code>sizeof()</code> operator.</p> <pre><code class="language-c">#include &lt;stdio.h&gt; struct Student { int roll_no; char name[50]; float marks; }; int main() { struct Student student1; student1.roll_no = 101; strcpy(student1.name, &quot;John Doe&quot;); student1.marks = 85.5; printf(&quot;Roll No: %d\n&quot;, student1.roll_no); printf(&quot;Name: %s\n&quot;, student1.name); printf(&quot;Marks: %.2f\n&quot;, student1.marks); printf(&quot;Size of struct Student: %zu bytes\n&quot;, sizeof(student1)); return 0; } </code></pre> Signup and view all the answers

<p>A structure variable can be initialized directly by providing values for its members, assigning values to its members after declaration, or by using a structure initializer, which offers a more concise way to initialize structure members during declaration.</p> <pre><code class="language-c">struct Student { int roll_no; char name[50]; float marks; }; int main() { // Initializing using structure initializer struct Student student1 = {101, &quot;John Doe&quot;, 85.5}; // Initializing each member one by one struct Student student2; student2.roll_no = 102; strcpy(student2.name, &quot;Alice Smith&quot;); student2.marks = 92.0; return 0; } </code></pre> Signup and view all the answers

<p>The main difference between structures and unions lies in the memory allocation.</p> <table> <thead> <tr> <th>Feature</th> <th>Structure</th> <th>Union</th> </tr> </thead> <tbody> <tr> <td>Memory Allocation</td> <td>Each member of a structure occupies its own memory space, resulting in the total size of the structure being the sum of the sizes of all its members.</td> <td>All members of a union share the same memory space. The size of the union is equal to the size of the largest member.</td> </tr> <tr> <td>Accessing Members</td> <td>All members can be accessed independently.</td> <td>Only one member can be accessed at a time. Accessing a member changes the value of that member, potentially overriding any existing values in the union.</td> </tr> <tr> <td>Usage</td> <td>Used when storing related data of different data types.</td> <td>Used to save memory when only one member of a set of members needs to be accessed at a time.</td> </tr> </tbody> </table> <pre><code class="language-c">#include &lt;stdio.h&gt; struct Student { int roll_no; char name[50]; float marks; }; union Employee { int emp_id; char dept[20]; float salary; }; int main() { struct Student student; union Employee employee; // structure initialization student.roll_no = 101; strcpy(student.name, &quot;John Doe&quot;); student.marks = 85.5; // union initialization employee.emp_id = 1234; strcpy(employee.dept, &quot;IT&quot;); printf(&quot;Student details: \n&quot;); printf(&quot;Roll No: %d\n&quot;, student.roll_no); printf(&quot;Name: %s\n&quot;, student.name); printf(&quot;Marks: %.2f\n&quot;, student.marks); printf(&quot;Employee details: \n&quot;); printf(&quot;Emp ID: %d\n&quot;, employee.emp_id); // This will print only the dept: IT printf(&quot;Department: %s\n&quot;, employee.dept); return 0; } </code></pre> Signup and view all the answers

<p>Dynamic memory allocation is the process of allocating memory during the execution of a program. This allows for flexibility in handling memory usage based on program needs. The most important functions associated with dynamic memory allocation include:</p> <ul> <li> <code>malloc()</code>: Allocates a block of memory of a specified size.</li> <li> <code>calloc()</code>: Allocates a block of memory and initializes all bytes to zero.</li> <li> <code>realloc()</code>: Changes the size of an existing memory block.</li> <li> <code>free()</code>: Releases a block of dynamically allocated memory back to the system.</li> </ul> Signup and view all the answers

<p><code>fopen()</code> is a standard library function in C used to open a file for reading, writing, or appending data. The mode argument specifies the operation to be performed on the file. The <code>fopen()</code> function returns a file pointer, which represents the connection to the file and is used for subsequent operations.</p> <pre><code class="language-c">#include &lt;stdio.h&gt; int main() { FILE *fptr; char str[] = &quot;This is a string to write to the file.\n&quot;; // Open the file in write mode ('w') fptr = fopen(&quot;myfile.txt&quot;, &quot;w&quot;); if (fptr == NULL) { printf(&quot;Error opening file!\n&quot;); return 1; } // Write string to the file fprintf(fptr, &quot;%s&quot;, str); fclose(fptr); printf(&quot;String written to file successfully!\n&quot;); return 0; } </code></pre> Signup and view all the answers

<p>File management refers to the process of creating, managing, and accessing files on computer systems. It involves tasks like creating new files, opening existing files, reading and writing data to files, renaming files, deleting files, and organizing files within a directory structure.</p> <p>The primary functions involved in file management include:</p> <ul> <li> <code>fopen()</code>: Opens a file for reading, writing, or appending data.</li> <li> <code>fclose()</code>: Closes a file that was previously opened with <code>fopen()</code>.</li> <li> <code>fread()</code>: Reads data from a file.</li> <li> <code>fwrite()</code>: Writes data to a file.</li> <li> <code>fgetc()</code>: Reads a single character from a file.</li> <li> <code>fputc()</code>: Writes a single character to a file.</li> <li> <code>fgets()</code>: Reads a line of text from a file (including newline character).</li> <li> <code>fputs()</code>: Writes a line of text to a file (including newline character).</li> <li> <code>fseek()</code>: Moves the file pointer to a specific position within a file.</li> <li> <code>ftell()</code>: Returns the current position of the file pointer.</li> <li> <code>rewind()</code>: Resets the file pointer to the beginning of a file.</li> <li> <code>remove()</code>: Deletes a file.</li> <li> <code>rename()</code>: Renames a file.</li> <li> <code>freopen()</code>: Reopens a file for a different mode of access.</li> <li> <code>feof()</code>: Checks if the end of a file has been reached.</li> <li> <code>ferror()</code>: Checks if an error occurred during a file operation.</li> </ul> Signup and view all the answers

<pre><code class="language-c">#include &lt;stdio.h&gt; int main() { FILE *fptr; // Open the file in write mode ('w') fptr = fopen(&quot;output.txt&quot;, &quot;w&quot;); if (fptr == NULL) { printf(&quot;Error opening file!\n&quot;); return 1; } // Write a single character to the file fputc('H', fptr); fputc('e', fptr); fputc('l', fptr); fputc('l', fptr); fputc('o', fptr); fputc('\n', fptr); // Write a newline character // Write a string to the file fputs(&quot;This is another line.\n&quot;, fptr); // Close the file fclose(fptr); printf(&quot;Data written to file successfully!\n&quot;); return 0; } </code></pre> Signup and view all the answers