ASCII is a character encoding used to represent text as binary. A computer does not store the letter A itself; it stores a binary pattern that represents th...
Question 1 Report
ASCII is a character encoding used to represent text as binary. A computer does not store the letter A itself; it stores a binary pattern that represents the character. The table gives some 7-bit ASCII codes. A programmer is checking text entered into a system and must convert between binary, denary and ASCII. Standard ASCII has codes from 0 to 127, although computers may store a code in an 8-bit byte by adding a leading zero. Use only the values in the table when answering character-code questions. Do not confuse a character’s denary ASCII value with its binary representation.
| Character | Denary ASCII | 7-bit binary ASCII |
|---|---|---|
| Space | 32 | 0100000 |
| A | 65 | 1000001 |
| B | 66 | 1000010 |
| C | 67 | 1000011 |
| a | 97 | 1100001 |
(a) Identify the character represented by the binary ASCII code 1000010. [1]
(b) Complete the table. [3]
| Character | Denary ASCII | 7-bit binary ASCII |
|---|---|---|
| A | 1000001 | |
| 66 | 1000010 | |
| Space | 32 |
(c) Convert the denary value 67 to an 8-bit binary pattern. [2]
(d) State the largest denary value that can be represented using 7 bits. [1]
(e) Give two benefits of using an agreed character encoding such as ASCII. [2]
(f) Explain why the ASCII codes for A and a are different. [3]
(g) Convert the 8-bit binary pattern 01100001 to denary and give its character from the table. [2]
Answer Details
(a) The code 1000010 represents B [1].
(b)
| Character | Denary ASCII | 7-bit binary ASCII |
|---|---|---|
| A | 65 | 1000001 |
| B | 66 | 1000010 |
| Space | 32 | 0100000 |
Each value follows directly from the supplied ASCII table [3].
(c) \(67=64+2+1\), so the 8-bit pattern is 01000011 [2].
(d) The largest 7-bit denary value is \(2^7-1=\textbf{127}\) [1].
(e) ASCII gives each character a standard, consistent code, allowing text to be stored, transmitted and interpreted consistently between compatible systems [2].
(f) Uppercase A and lowercase a are distinct characters. Each needs a unique ASCII pattern so the computer can distinguish the cases and reproduce the intended character [3].
(g) \(01100001_2=64+32+1=\textbf{97}\), which is a in the supplied table [2].
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