Questions and Answers
Which of the following statements correctly defines syntax in C?
Semantics determines how each statement affects program execution.
True
What is an example of a derived data type in C?
Structures
For dynamic memory allocation in C, the function used to allocate memory is ______.
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What is a memory leak?
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Which function is used to open a file in C?
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Match the following basic data types with their descriptions:
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The operation 'ptr++' increments the pointer to the next memory location of the pointed type.
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To change the size of dynamically allocated memory, use ______.
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Study Notes
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Syntax And Semantics
- Syntax defines the rules for structuring valid statements in C, ending with a semicolon (
;
). - Curly braces (
{}
) indicate the beginning and end of code blocks. - Semantics refers to the meaning behind syntactically correct statements and their impact on program behavior.
- Control structures such as
if
,for
, andwhile
exemplify semantics in action, along with function calls and expressions.
Data Types And Structures
-
Basic Data Types:
-
int
: Represents integer values with exampleint a = 5;
. -
float
: Represents single-precision floating-point numbers, e.g.,float b = 3.14;
. -
double
: Represents double-precision floating-point numbers, e.g.,double c = 2.71828;
. -
char
: Represents character values, e.g.,char d = 'A';
.
-
-
Derived Data Types:
-
Arrays: Collections of elements of the same data type, e.g.,
int arr[10];
. -
Structures (
struct
): Define a custom data type that groups different types, e.g.,struct Person { char name[20]; int age; };
. - Unions: Specialized structures that allow storing different data types in the same memory location, sharing space.
-
Arrays: Collections of elements of the same data type, e.g.,
Memory Management
- Static Memory Allocation: Allocated during compile time, where the size remains constant; applicable to global and local variables.
-
Dynamic Memory Allocation: Handled at runtime using functions like
malloc()
for memory allocation andcalloc()
for zero-initializing memory. -
realloc()
allows resizing previously allocated memory, whilefree()
deallocates memory to prevent memory leaks, which occur when allocated memory is not properly freed.
File Handling
-
File Operations:
-
fopen()
: Opens a file for reading or writing. -
fscanf()
,fgets()
,fread()
: Functions to read data from files. -
fprintf()
,fputs()
,fwrite()
: Functions to write data to files. -
fclose()
: Closes an opened file to free system resources.
-
-
File Modes:
-
"r"
: Opens a file in read mode. -
"w"
: Opens or creates a file in write mode, overwriting existing content. -
"a"
: Opens a file in append mode to add new data at the end. -
"rb"
and"wb"
: Open files in binary mode for reading or writing.
-
Pointer Arithmetic
-
Pointers: Variables designed to store memory addresses, declared with syntax like
int *ptr;
. -
Arithmetic Operations:
- Incrementing a pointer (e.g.,
ptr++
) advances it by the size of the type it points to, allowing traversal through arrays. - Subtracting two pointers yields the number of elements between them when both refer to the same array.
- Incrementing a pointer (e.g.,
- Pointers enhance the efficiency of handling arrays, strings, and dynamic memory allocation.
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