AS/A level - Computer Science - Chapter 1-Information Representation

1 Data Representation

Show understanding of binary magnitudes and the difference between binary prefixes and decimal prefixes
Understand the difference between and use:
•• kibi and kilo
•• mebi and mega
•• gibi and giga
•• tebi and tera
Show understanding of the basis of different number systems
Use the binary, denary, hexadecimal number bases and Binary Coded Decimal (BCD) and one’s and two’s complement representation for binary numbers
Convert an integer value from one number base / representation to another
Perform binary addition and subtraction: Using positive and negative binary integers. Show understanding of how overflow can occur.
Describe practical applications where Binary Coded
Decimal (BCD) and Hexadecimal are used
Show understanding of and be able to represent character data in its internal binary form, depending on the character set used
Familiar with ASCII (American Standard Code for Information Interchange), extended ASCII and Unicode. Students will not be expected to memorise any particular character codes. Use and understand the terms: pixel, file header,
image resolution, screen resolution, colour depth, bit depth
Perform calculations to estimate the file size for a bitmap image
Show understanding of the effects of changing elements of a bitmap image on the image quality and file size
Show understanding of how data for a vector graphic are encoded: Use the terms: drawing object, property, drawing list.
Justify the use of a bitmap image or a vector graphic for a given task.

2 Multimedia – Graphics and Sound.

Show understanding of how sound is represented and encoded: Use the terms: sampling, sampling rate, sampling resolution, analogue and digital data
Show understanding of how data for a bitmapped image are encoded.

3 Compression
Show understanding of the need for and examples of the use of compression
Show understanding of lossy and lossless compression and justify the use of a method in a given situation.
Show understanding of how a text file, bitmap image, vector graphic and sound file can be compressed Including the use of run-length encoding (RLE)