Symbols as Bits - ASCII Characters

Ok, so numbers are simply groups of bits.  What other objects will the computer's instructions manipulate?  How about the symbols that make up an alphabet?
It should come as no surprise that symbols that make up alphabets are just numbers, groups of bits, too.  But how do we know which numbers are used to represent which symbols, or characters as I'm going to call them from this point on?
It's all about standards.  In these lessons, we will use the American Standard Code for Information Interchange (ASCII) standard.  It is so ubiquious that it even has its own web page, www.asciitable.com.
Let's walk through a couple of examples, entries in the table.  Here are some characters, their decimal value and their binary value which is then transformed into an octal number.

        Uppercase 'A' = decimal 65 = binary 01000001 = 01 000 001 = octal 101
        Uppercase 'Z' = decimal 90 = binary 01011010 = 01 011 010 = octal 132
        The digit '1' = decimal 49 = binary 00110001 = 00 110 001 = octal 061
   

Table 1.4 is a small slice from the full ASCII character set, just enough to give you a flavor of its organization.

ASCII Character	in Binary	in Octal	in Decimal	in Hex
space	00100000	040	32	20
(	00101000	050	40	28
)	00101001	051	41	29
*	00101010	052	42	2A
0	00110000	060	48	30
1	00110001	061	49	31
2	00110010	062	50	32
9	00111001	071	57	39
A	01000001	101	65	41
B	01000010	102	66	42
C	01000011	103	67	43
Z	01011010	132	90	5A
a	01100001	141	97	61
b	01100010	142	98	62
c	01100011	143	99	63
z	01111010	172	122	7A
Table 1.4

Here's a little trivia, from days long past when computers were so slow (compared with today).

• Look closely at the binary representations of uppercase and lowercase letters.  You can convert uppercase to lowercase by turning on a single bit.  Or clearing the bit converts lowercase to uppercase.
• Clearing two bits will convert an ASCII digit to its numeric value.  Setting the same bits converts a number in the range 0...9 into its ASCII character representation.