Explain details about operators.
Operators can be defined as the symbols that help us to perform specific mathematical, relational, bitwise, conditional, or logical computations on operands. In other words, we can say that an operator operates the operands. For example, ‘+’ is an operator used for addition, as shown below:
c = a + b;
Here, ‘+’ is the operator known as the addition operator, and ‘a’ and ‘b’ are operands. The addition operator tells the compiler to add both of the operands ‘a’ and ‘b’. The functionality of the C programming language is incomplete without the use of operators.
C has many built-in operators and can be classified into 6 types:
Arithmetic Operators.Relational Operators,Logical Operators,Bitwise Operators,Assignment Operators
1. Arithmetic Operations in C
These operators are used to perform arithmetic/mathematical operations on operands. Examples: (+, -, *, /, %,++,–).
2. Relational Operators in C
These are used for the comparison of the values of two operands. For example, checking if one operand is equal to the other operand or not, whether an operand is greater than the other operand or not, etc. Some of the relational operators are (==, >= , <= )
3. Logical Operator in C
Logical Operators are used to combining two or more conditions/constraints or to complement the evaluation of the original condition in consideration. The result of the operation of a logical operator is a Boolean value either true or false.
For example, the logical AND represented as the ‘&&’ operator in C returns true when both the conditions under consideration are satisfied. Otherwise, it returns false. Therefore, a && b returns true when both a and b are true
4. Bitwise Operators in C
The Bitwise operators are used to perform bit-level operations on the operands. The operators are first converted to bit-level and then the calculation is performed on the operands. Mathematical operations such as addition, subtraction, multiplication, etc.
can be performed at the bit level for faster processing. For example, the bitwise AND operator represented as ‘&’ in C takes two numbers as operands and does AND on every bit of two numbers. The result of AND is 1 only if both bits are 1(True).
5. Assignment Operators in C
Assignment operators are used to assign value to a variable. The left side operand of the assignment operator is a variable and the right side operand of the assignment operator is a value. The value on the right side must be of the same data type as the variable on the left side otherwise the compiler will raise an error.
What is multidimensional array
A multi-dimensional array can be termed as an array of arrays that stores homogeneous data in tabular form. Data in multidimensional arrays is generally stored in row-major order in the memory.
The general form of declaring N-dimensional arrays is shown below.
Syntax:
data_type array_name[size1][size2]....[sizeN];
The most commonly used forms of the multidimensional array are:
Two Dimensional Array
Three Dimensional Array
Two-Dimensional Array in C
A two-dimensional array or 2D array in C is the simplest form of the multidimensional array. We can visualize a two-dimensional array as an array of one-dimensional arrays arranged one over another forming a table with ‘x’ rows and ‘y’ columns where the row number ranges from 0 to (x-1) and the column number ranges from 0 to (y-1)
Three-Dimensional Array in C
A Three Dimensional Array or 3D array in C is a collection of two-dimensional arrays. It can be visualized as multiple 2D arrays stacked on top of each other.
Explain about error handling
Although C does not provide direct support to error handling (or exception handling), there are ways through which error handling can be done in C. A programmer has to prevent errors at the first place and test return values from the functions.
A lot of C function calls return a -1 or NULL in case of an error, so quick test on these return values are easily done with for instance an ‘if statement’. For example, In Socket Programming, the returned value of the functions like socket(), listen() etc. are checked to see if there is an error or not.
Different methods of Error handling in C
Global Variable errno: When a function is called in C, a variable named as errno is automatically assigned a code (value) which can be used to identify the type of error that has been encountered. Its a global variable indicating the error occurred during any function call and defined in the header file errno.h.
Different codes (values) for errno mean different types of errors.
perror() and strerror(): The errno value got above indicate the types of error encountered.
If it is required to show the error description, then there are two functions that can be used to display a text message that is associated with errorno.
Exit Status: The C standard specifies two constants: EXIT_SUCCESS and EXIT_FAILURE, that may be passed to exit() to indicate successful or unsuccessful termination, respectively. These are macros defined in stdlib.h.
Divide by Zero Errors: A common pitfall made by C programmers is not checking if a divisor is zero before a division command. Division by zero leads to undefined behavior, there is no C language construct that can do anything about it. Your best bet is to not divide by zero in the first place, by checking the denominator.
Briefly explain about various storage classes in c
Storage Classes are used to describe the features of a variable/function. These features basically include the scope, visibility and life-time which help us to trace the existence of a particular variable during the runtime of a program.
C language uses 4 storage classes, namely:
auto: This is the default storage class for all the variables declared inside a function or a block. Hence, the keyword auto is rarely used while writing programs in C language. Auto variables can be only accessed within the block/function they have been declared and not outside them (which defines their scope).
Of course, these can be accessed within nested blocks within the parent block/function in which the auto variable was declared. However, they can be accessed outside their scope as well using the concept of pointers given here by pointing to the very exact memory location where the variables reside. They are assigned a garbage value by default whenever they are declared.
extern: Extern storage class simply tells us that the variable is defined elsewhere and not within the same block where it is used. Basically, the value is assigned to it in a different block and this can be overwritten/changed in a different block as well. So an extern variable is nothing but a global variable initialized
with a legal value where it is declared in order to be used elsewhere. It can be accessed within any function/block. Also, a normal global variable can be made extern as well by placing the ‘extern’ keyword before its declaration/definition in any function/block. This basically signifies that we are not initializing a new variable but instead we are using/accessing the global variable only.
The main purpose of using extern variables is that they can be accessed between two different files which are part of a large program. For more information on how extern variables work, have a look at this link.
static: This storage class is used to declare static variables which are popularly used while writing programs in C language. Static variables have the property of preserving their value even after they are out of their scope! Hence, static variables preserve the value of their last use in their scope. So we can say that they are initialized only once and exist till the termination of the program.
Thus, no new memory is allocated because they are not re-declared. Their scope is local to the function to which they were defined. Global static variables can be accessed anywhere in the program. By default, they are assigned the value 0 by the compiler.
register: This storage class declares register variables that have the same functionality as that of the auto variables. The only difference is that the compiler tries to store these variables in the register of the microprocessor if a free register is available. This makes the use of register variables to be much faster than that of the variables stored in the memory during the runtime of the program.
If a free registration is not available, these are then stored in the memory only. Usually few variables which are to be accessed very frequently in a program are declared with the register keyword which improves the running time of the program. An important and interesting point to be noted here is that we cannot obtain the address of a register variable using pointers.
Write about pointer and structure in c
A structure pointer is defined as the pointer which points to the address of the memory block that stores a structure known as the structure pointer.
Complex data structures like Linked lists, trees, graphs, etc. are created with the help of structure pointers.
The structure pointer tells the address of a structure in memory by pointing the variable to the structure variable.
Accessing the Structure Member with the Help of Pointers
There are two ways to access the members of the structure with the help of a structure pointer:
With the help of (*) asterisk or indirection operator and (.) dot operator.
With the help of ( -> ) Arrow operator.
Discuss about defining and accessing a function in c
Functions are sets of statements that take inputs, perform some operations, and produce results. The operation of a function occurs only when it is called.
Rather than writing the same code for different inputs repeatedly, we can call the function instead of writing the same code over and over again.
Function Declarations:
Function declarations tell the compiler how many parameters a function takes, what kinds of parameters it returns, and what types of data it takes.
Function declarations do not need to include parameter names, but definitions must.
Function Arguments and Return values
A function is all dependent upon what value it will return and what arguments are been passed.
Function Call:
To Call a function parameters are passed along the function name. In the below example, the first sum function is called and 10,30 are passed to the sum function.
After the function call sum of a and b is returned and control is also returned back to the main function of the program.
Functions that the programmer creates are known as User-Defined functions or “tailor-made functions”. User-defined functions can be improved and modified according to the need of the programmer.
Whenever we write a function that is case-specific and is not defined in any header file, we need to declare and define our own functions according to the syntax.
Explain about dynamic memory allocation in c
Since C is a structured language, it has some fixed rules for programming. One of them includes changing the size of an array. An array is a collection of items stored at contiguous memory locations.
As it can be seen that the length (size) of the array above made is 9. But what if there is a requirement to change this length (size). For Example,
If there is a situation where only 5 elements are needed to be entered in this array. In this case, the remaining 4 indices are just wasting memory in this array. So there is a requirement to lessen the length (size) of the array from 9 to 5.
Take another situation. In this, there is an array of 9 elements with all 9 indices filled. But there is a need to enter 3 more elements in this array. In this case, 3 indices more are required. So the length (size) of the array needs to be changed from 9 to 12.
This procedure is referred to as Dynamic Memory Allocation in C.
Therefore, C Dynamic Memory Allocation can be defined as a procedure in which the size of a data structure (like Array) is changed during the runtime.
C provides some functions to achieve these tasks. There are 4 library functions provided by C defined under header file to facilitate dynamic memory allocation in C programming. They are:
malloc(),calloc().free(),realloc()
The “malloc” or “memory allocation” method in C is used to dynamically allocate a single large block of memory with the specified size. It returns a pointer of type void which can be cast into a pointer of any form. It doesn’t Initialize memory at execution time so that it has initialized each block with the default garbage value initially.
“calloc” or “contiguous allocation” method in C is used to dynamically allocate the specified number of blocks of memory of the specified type. it is very much similar to malloc() but has two different points
“free” method in C is used to dynamically de-allocate the memory. The memory allocated using functions malloc() and calloc() is not de-allocated on their own. Hence the free() method is used, whenever the dynamic memory allocation takes place. It helps to reduce wastage of memory by freeing it.
“realloc” or “re-allocation” method in C is used to dynamically change the memory allocation of a previously allocated memory. In other words, if the memory previously allocated with the help of malloc or calloc is insufficient, realloc can be used to dynamically re-allocate memory. re-allocation of memory maintains the already present value and new blocks will be initialized with the default garbage value.
Discuss about file i/o operations in c
A single C file can read, write, move, and create files in our computer easily using a few functions and elements included in the C File I/O system. We can easily manipulate data in a file regardless of whether the file is a text file or a binary file using functions like fopen(), fclose(), fprintf(), fscanf(), getc(), putc(), getw(), fseek(), etc.
A file is used to store huge data. C provides multiple file management functions like file creation, opening and reading files, Writing to the file, and closing a file. The file is used to store relevant data and file handling in C is used to manipulate the data.
Types of Files in C
There are mainly two types of files that can be handled using File Handling in C as mentioned below:
Text Files
Binary Files
Text Files:
These are simple text files that are saved by the (.txt) extension and can be created or modified by any text editor. Text file stores data in the form of ASCII characters and is used to store a stream of characters.
Binary Files:
It is stored in binary format instead of ASCII characters. Binary files are normally used to store numeric Information (int, float, double). Here data is stored in binary form i.e, (0’s and 1’s).
