DEV Community: Alpha_Edit

I am Starting #100daysofcode !

Alpha_Edit — Mon, 19 Apr 2021 04:33:06 +0000

Hello folks,
I am starting #100daysofcode! I will be posting the daily update in dev.to. Make sure to follow me to get the update of the blog i post.
I also have a github repo of all the side projects i do in 100 days.

Codely-F / 100daysofcode

This is the repo for #100daysofcode challenge.

Let the challenge begin!

C Programming Cheat Sheet - 6

Alpha_Edit — Sun, 11 Apr 2021 14:09:56 +0000

6 Strings

6.1 What is String?

Strings are arrays of characters. Each member of array contains one of characters in the string.

Example

#include<stdio.h> 
main() 
{ 
    char name[20]; 
    printf("Enter your name : "); 
    scanf("%s",name); 
    printf("Hello, %s , how are you ?\n",name); 
}

Output Results:

Enter your name : Vineet 
Hello, Vineet, how are you ?

If user enters "Vineet" then the first member of array will contain 'V' , second cell will contain 'i' and so on. C determines end of a string by a zero value character. We call this character as NULL character and show it with \0 character. (It's only one character and its value is 0, however we show it with two characters to remember it is a character type, not an integer).

Equally we can make that string by assigning character values to each member.

name[0]='B'; 
name[1]='r'; 
name[2]='i'; 
name[3]='a'; 
name[4]='n'; 
name[5]='\0';

As we saw in above example placeholder for string variables is %s. Also we will not use a & sign for receiving string values.

6.2 Point to Note

While entering the string using scanf() we must be cautious about
two things:

* The length of the string should not exceed the dimension of the character array. This is because the C compiler doesn’t perform bounds checking on character arrays.
* `scanf()` is not capable of receiving multi-word strings. Therefore names such as "Vineet Choudhary" would be unacceptable. The way to get around this limitation is by using the function `gets()`.The usage of functions `gets()` and its counter part `puts()` is shown below.

#include<stdio.h> 
main( ) 
{ 
    char name[25] ; 
    printf ("Enter your full name ") ; 
    gets (name) ; 
    puts ("Hello!") ; 
    puts (name) ; 
}

And here is the output...

Enter your name Vineet Choudhary 
Hello! 
Vineet Choudhary

The program and the output are self-explanatory except for the fact that, puts() can display only one string at a time (hence the use of two puts() in the program above). Also, on displaying a string, unlike printf(), puts() places the cursor on the next line. Though gets() is capable of receiving only one string at a time, the plus point with gets() is that it can receive a multi-word string.

If we are prepared to take the trouble we can make scanf() accept multi-word strings by writing it in this manner:

char name[25] ; 
printf ("Enter your full name ") ; 
scanf ("%[^\n]s", name) ;

Though workable this is the best of the ways to call a function, you would agree.

6.3 Standard Library String Functions

With every C compiler a large set of useful string handling library functions are provided in string.h file.

* `strlen` - Finds length of a string
* `strlwr` - Converts a string to lowercase
* `strupr` - Converts a string to uppercase
* `strcat` - Appends one string at the end of another
* `strncat` - Appends first n characters of a string at the end of
another
* `strcpy` - Copies a string into another
* `strncpy` - Copies first n characters of one string into another
* `strcmp` - Compares two strings
* `strncmp` - Compares first n characters of two strings
* `strcmpi` - Compares two strings without regard to case ("i" denotes
that this function ignores case)
* `stricmp` - Compares two strings without regard to case (identical to
strcmpi)
* `strnicmp` - Compares first n characters of two strings without regard
to case
* `strdup` - Duplicates a string
* `strchr` - Finds first occurrence ofa given character in a string
* `strrchr` - Finds last occurrence ofa given character in a string
* `strstr` - Finds first occurrence of a given string in another string
* `strset` - Sets all characters ofstring to a given character
* `strnset` - Sets first n characters ofa string to a given character
* `strrev` - Reverses string

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C Programming Cheat Sheet - 5

Alpha_Edit — Sat, 10 Apr 2021 05:29:48 +0000

Here is the C Programming Cheat - 5

5. Arrays

Arrays are structures that hold multiple variables of the same data type. The first element in the array is numbered 0, so the last element is 1 less than the size of the array. An array is also known as a sub scripted variable. Before using an array its type and dimension must be declared.

5.1 Array Declaration

Like other variables an array needs to be declared so that the compiler will know what kind of an array and how large an array we want.

int marks[30] ;

Here, int specifies the type of the variable, just as it does with ordinary variables and the word marks specifies the name of the variable. The [30] however is new. The number 30 tells how many elements of the type int will be in our array. This number is often called the "dimension" of the array. The bracket ( [ ] ) tells the compiler that we are dealing with an array.

Let us now see how to initialize an array while declaring it. Following are a few examples that demonstrate this.

int num[6] = { 2, 4, 12, 5, 45, 5 } ; 
int n[] = { 2, 4, 12, 5, 45, 5 } ; 
float press[] = { 12.3, 34.2 -23.4, -11.3 } ;

5.2 Accessing Elements of an Array

Once an array is declared, let us see how individual elements in the array can be referred. This is done with subscript, the number in the brackets following the array name. This number specifies the element’s position in the array. All the array elements are numbered, starting with 0. Thus, marks [2] is not the second element of the array, but the third.

int valueOfThirdElement = marks[2];

5.3 Entering Data into an Array

Here is the section of code that places data into an array:

for(i = 0;i <= 29;i++) 
{ 
    printf("\nEnter marks "); 
    scanf("%d", &marks[i]); 
}

The for loop causes the process of asking for and receiving a student’s marks from the user to be repeated 30 times. The first time through the loop, i has a value 0, so the scanf() function will cause the value typed to be stored in the array element marks[0], the first element of the array. This process will be repeated until i becomes 29. This is last time through the loop, which is a good thing, because there is no array element like marks[30].

In scanf() function, we have used the "address of" operator (&) on the element marks[i] of the array. In so doing, we are passing the address of this particular array element to the scanf() function, rather than its value; which is what scanf() requires.

5.4 Reading Data from an Array

The balance of the program reads the data back out of the array and uses it to calculate the average. The for loop is much the same, but now the body of the loop causes each student’s marks to be added to a running total stored in a variable called sum. When all the marks have been added up, the result is divided by 30, the number of students, to get the average.

for ( i = 0 ; i <= 29 ; i++ )
    sum = sum + marks[i] ; 
avg = sum / 30 ; 
printf ( "\nAverage marks = %d", avg ) ;

5.5 Example

Let us try to write a program to find average marks obtained by a
class of 30 students in a test.

#include<stdio.h>  
main() 
{ 
    int avg, i, sum=0; 
    int marks[30] ; /*array declaration */ 
    for ( i = 0 ; i <= 29 ; i++ ) 
    { 
        printf ( "\nEnter marks " ) ; 
        scanf ( "%d", &marks[i] ) ; /* store data in array */ 
    } 
    for ( i = 0 ; i <= 29 ; i++ ) 
        sum = sum + marks[i] ; /* read data from an array*/ 
    avg = sum / 30 ; 
    printf ( "\nAverage marks = %d", avg ) ; 
}

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C Programming Cheat Sheet -4

Alpha_Edit — Fri, 09 Apr 2021 10:19:41 +0000

4.The Loop Control Structure

Sometimes we want some part of our code to be executed more than once. We can either repeat the code in our program or use loops instead. It is obvious that if for example we need to execute some part of code for a hundred times it is not practical to repeat the code. Alternatively we can use our repeating code inside a loop.

There are three methods for, while and do-while which we can repeat a part of a program.

4.1 while loop

while loop is constructed of a condition or expression and a single command or a block of commands that must run
in a loop.

//for single statement  
while(expression) 
    statement;

//for multiple statement   
while(expression) 
{ 
    block of statement 
}

The statements within the while loop would keep on getting executed till the condition being tested remains true. When the condition becomes false, the control passes to the first statement that follows the body of the while loop.
The general form of while is as shown below:

initialise loop counter;  
while (test loopcounter using a condition) 
{ 
    do this; 
    and this; 
    increment loopcounter;
}

4.2 for loop

for loop is something similar to while loop but it is more complex. for loop is constructed from a control statement that determines how many times the loop will run and a command section. Command section is either a single command or a block of commands.

//for single statement  
for(control statement) 
    statement;  

//for multiple statement
for(control statement) 
{ 
    block of statement 
}

Control statement itself has three parts:

for ( initialization; test condition; run every time command )

* `Initialization` part is performed only once at `for` loop start. We can initialize a loop variable here.
* `Test condition` is the most important part of the loop. Loop will continue to run if this condition is valid (true). If the condition becomes invalid (false) then the loop will terminate.
* `Run every time command` section will be performed in every loop cycle. We use this part to reach the final condition for terminating the loop. **For example** we can increase or decrease loop variable’s value in a way that after specified number of cycles the loop condition becomes invalid and `for` loop can terminate.

4.3 do-while loop

The while and for loops test the termination condition at the top. By contrast, the third loop in C, the do-while, tests at the bottom after making each pass through the loop body; the body is always executed at least once.
The syntax of the do is

do
{
    statements;
}while (expression);

The statement is executed, then expression is evaluated. If it is true, statement is evaluated again, and so on. When the expression becomes false, the loop terminates. Experience shows that do-while is much less used than while and for. A do-while loop is used to ensure that the statements within the loop are executed at least once.

4.4 Break and Continue statement

We used break statement in switch...case structures in previously. We can also use "break" statement inside loops to terminate a loop and exit it (with a specific condition).

In above example loop execution continues until either num>=20 or entered score is negative.

while (num<20) 
{ 
    printf("Enter score : "); 
    scanf("%d",&scores[num]); 
    if(scores[num]<0) 
        break; 
}

Continue statement can be used in loops. Like break command continue changes flow of a program. It does not terminate the loop however. It just skips the rest of current iteration of the loop and returns to starting point of the loop.

#include<stdio.h> 
main() 
{ 
    while((ch=getchar())!='\n') 
    { 
        if(ch=='.') 
            continue; 
        putchar(ch); 
    }  
}

In above example, program accepts all input but omits the '.' character from it. The text will be echoed as you enter it but the main output will be printed after you press the enter key (which is equal to inserting a "\n" character) is pressed. As we told earlier this is because getchar() function is a buffered input function.

4.5 Goto and labels

C provides the infinitely-abusable goto statement, and labels to branch to. Formally, the goto statement is never necessary, and in practice it is almost always easy to write code without it. We have not used goto in this book.

Nevertheless, there are a few situations where gotos may find a place. The most common is to abandon processing in some deeply nested structure, such as breaking out of two or more loops at once. The break statement cannot be used directly since it only exits from the innermost loop. Thus:

for ( ... )
{           
    for ( ... ) 
    {               
        ...               
        if (disaster)
        {                   
            goto error;
        }           
    }
}       
...   
error:       
/* clean up the mess */

This organization is handy if the error-handling code is non-trivial, and if errors can occur in several places.

A label has the same form as a variable name, and is followed by a colon. It can be attached to any statement in the same function as the goto. The scope of a label is the entire function.

Note - By uses of goto, programs become unreliable, unreadable, and hard to debug. And yet many programmers find goto seductive.

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C Programming Cheat Sheet - 3

Alpha_Edit — Tue, 06 Apr 2021 08:39:26 +0000

3.The Decision Control Structure

C has three major decision making instructions—the if statement, the if-else statement, and the switch statement.

3.1 The If Statement

C Uses The keyword if to implement the decision control instruction. The general form of if statement looks like this:

//for single statement
if(condition) 
    statement;

//for multiple statement
if(condition) 
{ 
    block of statement; 
}

The more general form is as follow:

//for single statement
if(expression) 
    statement;

//for multiple statement
if(expression) 
{ 
    block of statement; 
}

Here the expression can be any valid expression including a relational expression. We can even use arithmetic expressions in the if statement. For example all the following if statements are valid

if (3 + 2 % 5) 
    printf("This works");

The expression (3 + 2 % 5) evaluates to 5 and since 5 is non-zero it is considered to be true. Hence the printf("This works"); gets executed.

3.2 The If-Else Statement

The if statement by itself will execute a single statement, or a group of statements, when the expression following if evaluates to true. It does nothing when the expression evaluates to false. Can we execute one group of statements if the expression evaluates to true and another group of statements if the expression evaluates to false? Of course! This is what is the purpose of the else statement that is demonstrated as

if (expression)
{ 
    block of statement;
}
else
    statement;

Note

The group of statements after the ifupto and not including the else is called an if block. Similarly, the statement after the else form the else block.
Notice that the else is written exactly below the if. The statements in the if block and those in the else block have been indented to the right.
Had there been only one statement to be executed in the if block and only one statement in the else block we could have dropped the pair of braces.
As with the if statement, the default scope of else is also the statement immediately after the else. To override this default scope a pair of braces as shown in the above "Multiple Statements within if" must be used.

3.3 Nested if-else

If we write an entire if-else construct within either the body of the if statement or the body of an else statement. This is called nesting of ifs. This is demonstrated as -

if (expression1)
    statement;
else 
{
    if (expression2)
        statement;  
    else
    { 
        block of statement;
    }
}

3.4 The if-else Ladder/else-if Clause

The else-if is the most general way of writing a multi-way decision.

if(expression1) 
    statement; 
else if(expression2) 
    statement; 
else if(expression3) 
    statement; 
else if(expression4) 
{ 
    block of statement; 
} 
else 
    statement;

The expressions are evaluated in order; if an expressions true, the "statement" or "block of statement" associated with it is executed, and this terminates the whole chain. As always, the code for each statement is either a single statement, or a group of them in braces. The last else part handles the "none of the above" or default case where none of the other conditions is satisfied.

3.5 Switch Statements or Control Statements

The switch statement is a multi-way decision that tests whether an expression matches one of a number of constant integer values, and branches accordingly. The switch statement that allows us to make a decision from the number of choices is called a switch, or more correctly switch-case-default, since these three keywords go together to make up the switch statement.

switch (expression) 
{
    case constant-expression: 
        statement1;
        statement2;
        break;
    case constant-expression: 
        statement;
        break;
    ...
    default: 
        statement;
}

In switch…case command, each case acts like a simple label. A label determines a point in program which execution must continue from there. Switch statement will choose one of case sections or labels from where the execution of the program will continue. The program will continue execution until it reaches break command.
- break statements have vital rule in switch structure. If you remove these statements, program execution will continue to next case sections and all remaining case sections until the end of switch block will be executed (while most of the time we just want one case section to be run).
- default section will be executed if none of the case sections match switch comparison.

3.6 switch Versus if-else Ladder

There are some things that you simply cannot do with a switch.
These are:

*  A float expression cannot be tested using a switch
* Cases can never have variable expressions (for example it is wrong to say `case a +3` )
* Multiple cases cannot use same expressions.

C Programming Cheat Sheet - 2

Alpha_Edit — Tue, 06 Apr 2021 07:01:37 +0000

Here is the C Programming Cheat Sheet - Part 2

2.Expression & Operators Precedence

Following table summarizes the rules for precedence and associativity of all operators, including those that we have not yet discussed. Operators on the same line have the same precedence; rows are in order of decreasing precedence, so, for example, *, /, and % all have the same precedence, which is higher than that of binary + and -. The ``operator'' () refers to function call. The operators -> and . are used to access members of structures;

Description	Operators	Associativity
Function Expression	()	Left to Right
Array Expression	[]	Left to Right
Structure Operator	->	Left to Right
Structure Operator	.	Left to Right
Unary minus	-	Right to Left
Increment/Decrement	++, --	Right to Left
One’s compliment	~	Right to Left
Negation	!	Right to Left
Address of	&	Right to Left
Value of address	'*'	Right to Left
Type cast	(type)	Right to Left
Size in bytes	sizeof	Right to Left
Multiplication	'*'	Left to Right
Division	/	Left to Right
Modulus	%	Left to Right
Addition	+	Left to Right
Subtraction	-	Left to Right
Left Shift	<<	Left to Right
Right Shift	>>	Left to Right
Less Than	<	Left to Right
Less Than or Equal to	<+	Left to Right
Greater Than	>	Left to Right
Greater Than or equal	>+	Left to Right
Equal to	==	Left to Right
Not equal to	!=	Left to Right
Bitwise AND	&	Left to Right
Bitwise exclusive OR	^	Left to Right
Logical AND	&&	Left to Right
Conditional	?:	Left to Right
Assignment	=, *=, /=, %=, +=, -=, &=, ^=, =, <<=, >>=	Left to Right
Comma	,	Right to Left

C Programming Cheat Sheet

Alpha_Edit — Wed, 31 Mar 2021 04:25:57 +0000

Here is a Cheat Sheet for C Programming Language.

1. About C Programming Language.

1.1 What is C Programming Language?

C programming language was developed in 1972 by Dennis Ritchie at bell laboratories of AT&T (American Telephone & Telegraph), located in the U.S.A.

1.2 Why was C programming language was developed?

It was developed to overcome the problems of previous languages such as B, BCPL, etc. Initially, C language was developed to be used in UNIX operating system. It inherits many features of previous languages such as B and BCPL.

1.3 Features of C Programming Language.

Structured language.
General purpose language.
Portability.
Code Re-usability & Ability to customize and extend.
Limited Number of Key Word.
Mid-level programming language.

1.4 C program Structure.

pre-processor directives
global declarations

main()
{
    local variable deceleration
    statement sequences
    function invoking
}

1.5 C Keywords

Keywords are the words whose meaning has already been explained to the C compiler. There are only 32 keywords available in C. The keywords are also called ‘Reserved words’. When the current programming language is C or C++, these keywords cannot be abbreviated, used as variable names, or used as any other type of identifiers.

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

1.6 C Character Set

The C character set consists of upper and lowercase alphabets, digits, special characters and white spaces, altogether called as the alphanumeric character. This can denotes any alphabet, digit or special symbol used to represent information. Following are the valid alphabets, numbers and special symbols allowed in C.

1.7 Rules for Writing, Compiling and Executing the C program

C is case sensitive means variable named "COUNTER" is different from a variable named "counter".
- All keywords are lower cased.
- Keywords cannot be used for any other purpose (like variable names).
- Every C statement must end with a ;. Thus ;acts as a statement terminator.
- First character must be an alphabet or underscore, no special symbol other than an underscore, no commas or blank spaces are allowed with in a variable, constant or keyword.
- Blank spaces may be inserted between two words to improve the readability of the statement. However, no blank spaces are allowed within a variable, constant or keyword.
- Variable must be declared before it is used in the program.
- File should be have the extension .c
- Program need to be compiled before execution.

1.8 Data types & Placeholders

C has 5 basic built-in data types.
Data type defines a set of values that a variable can store along with a set of operations that can be performed on it.
A variable takes different values at different times.
General form for declaring a variable is: type name;.
An example for using variables comes below:

main() 
{ 
    int sum; 
    sum=12; 
    sum=sum+5; 
    printf("Sum is %d",sum); 
}

printf function will print the following:
Sum is 17
In fact %d is the placeholder for integer variable value that its name comes after double quotes.

Common data types are:
- int - integer
- char - character
- long - long integer
- float - float number
- double - long float
Other placeholders are:

Placeholders        Format
%c                  Character
%d                  Signed decimal integer
%i                  Signed decimal integer
%e                  Scientific notation[e]
%E                  Scientific notation[E]
%f                  Decimal floating point
%o                  unsigned octal
%s                  String of character
%u                  unsigned decimal integer
%x                  unsigned Hexadecimal (lower)
%X                  unsigned Hexadecimal (upper)
%p                  dispaly a pointer
%%                  print a %

1.9 Control characters (Escape sequences)

Certain non printing characters as well as the backslash () and the apostrophe('), can be expressed in terms of escape sequence.

\a - Bell
\n - New line
\r - Carriage return
\b - Backspace
\f - Formfeed
\t - Horizontal tab
\" - Quotation mark
\v - Vertical tab
\' - Apostrophe
\\ - Backslash
\? - Question mark
\0 - Null

1.10 Receiving input values from keyboard

scanf function used to receiving input from keyboard.
General form of scanf function is :

scanf("Format string",&variable,&variable,...);

Format string contains placeholders for variables that we intend to receive from keyboard. A & sign comes before each variable name that comes in variable listing. Character strings are exceptions from this rule. They will not come with this sign before them.

Note: You are not allowed to insert any additional characters in format string other than placeholders and some special characters. Entering even a space or other undesired character will cause your program to work incorrectly and the results will be unexpected. So make sure you just insert placeholder characters in scanf format string. The following example receives multiple variables from keyboard.

float a; 
int n; 
scanf("%d%f",&n,&a);

Pay attention that scanf function has no error checking capabilities built in it. Programmer is responsible for validating input data (type, range etc.) and preventing errors

What browser do you use for programming?

Alpha_Edit — Thu, 18 Mar 2021 03:59:41 +0000

I use Firefox and Chrome.
I am curious to know what browser do you use

Best Websites to find what technology the website is using

Alpha_Edit — Tue, 09 Mar 2021 06:35:17 +0000

Have you ever been in a situation, where you need to find what tech the website is using to follow it?

Here are the 2 websites which i use to find the tech the website is using

1. What Cms

This Website finds What Content Management system the website use or what hosting provider the website use or if the website use WordPress or Shopify, this can find the theme the website is using.

2. W3 Techs

This website gives information from the language used in the website and it is very useful when the website is not a CMS website.

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