C Array Count (Beginner) [duplicate]

Answer 1

In C, when you have a variable c of type char, it actually stores some integer encoding of the char (usually the ASCII code). So c-'0' means the difference of the code of the character contained in c and the character 0. Since the digits are in natural order it convert the digit in the associated number.

Answer 2

The C standard requires that the characters '0' to '9' have consecutive values.

'0' represents the value zero as a character and c is the value you enter it calculates to be like this :

'1' - '0' == 1

'2' - '0' == 2

and so on ... i.e equal to the value of c if c is a digit

Answer 3

You asked how the below expression works

 c-'0'

The ASCII code of the entered charecter is subtracted from the ASCII code of 0 and it defines the position in the array where the count has to be stored .

Suppose you enter 1 from the keyboard ASCII code for 1 is 49 and ASCII code for 0 is 48. hence

   49-48 =1 

and the count will be stored in the array index location 1 .

Answer 4

Ascii is an encoding which gives consecutive id's to consecutive digits. As Eric Postpischil pointed out, the standard demands that property, even though the underlying encoding need not be ascii. Ascii is quite common though.

char c1 = '0';
char c2 = '1';

So whatever number '0' is mapped to, '1' will be that number + 1. In essence:

c2 == c1 + 1

Subtracting '0' from a character which is a digit, will return its numeric value:

'1' - '0' == 1

Answer 5

'0' is a char and it has value 48. You can look up any ASCII table in the google. It works this way because you read from the input char value not the int, so if you don't add "-'0'" part it will increment 48th cell of an array. Instead of "-'0'" you can put "-48", in my opinion it's more readable this way.

Answer 6

Loog at ASCII wikipedia.

The American Standard Code for Information Interchange (ASCII /ˈæski/ ass-kee)1 is a character-encoding scheme originally based on the English alphabet that encodes 128 specified characters - the numbers 0-9, the letters a-z and A-Z, some basic punctuation symbols, some control codes that originated with Teletype machines, and a blank space - into the 7-bit binary integers.

So In the ASCII Scheme the '0' char is the number 48, the char '1' is 41, and so on. So c - '0' is equivalent to c - 48. If c is '1' the expression became 49 - 48 = 1. So in few word 'c' - '0' convert a digit char ['0'-'9'] into an integer [0-9].

Edit 1 As suggested by @Eric Postpischil, ASCII is not part of ANSi C (nor c++). But is very common and all compiler I know use ASCII set.