1 Information representation

1.1 Data Representation

Candidates should be able to:

1. Show understanding of binary magnitudes and the difference between binary prefixes and decimal prefixes

   Notes and guidance

   Understand the difference between and use:

   • kibi and kilo
   • mebi and mega
   • gibi and giga
   • tebi and tera

2. Show understanding of different number systems

   Notes and guidance

   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

3. Perform binary addition and subtraction

   Notes and guidance

   Using positive and negative binary integers

   Show understanding of how overflow can occur

4. Describe practical applications where Binary Coded Decimal (BCD) and Hexadecimal are used

5. Show understanding of and be able to represent character data in its internal binary form, depending on the character set used

   Notes and guidance

   Students are expected to be familiar with ASCII (American Standard Code for Information Interchange), extended ASCII and Unicode.

   Students will not be expected to memorise any particular character codes

1.2 Multimedia

Candidates should be able to:

1. Show understanding of how data for a bitmapped image are encoded

   Notes and guidance

   Use and understand the terms: pixel, file header, image resolution, screen resolution, colour depth/ bit depth

2. Perform calculations to estimate the file size for a bitmap image
3. Show understanding of the effects of changing elements of a bitmap image on the image quality and file size

   Notes and guidance

   Use the terms: image resolution, colour depth / bit depth

4. Show understanding of how data for a vector graphic are encoded

   Notes and guidance

   Use the terms: drawing object, property, drawing list

5. Justify the use of a bitmap image or a vector graphic for a given task
6. Show understanding of how sound is represented and encoded

   Notes and guidance

   Use the terms: sampling, sampling rate, sampling resolution, analogue and digital data

7. Show understanding of the impact of changing the sampling rate and resolution

   Notes and guidance

   Including the impact on file size and accuracy

1.3 Compression

Candidates should be able to:

1. Show understanding of the need for and examples of the use of compression
2. Show understanding of lossy and lossless compression and justify the use of a method in a given situation
3. Show understanding of how a text file, bitmap image, vector graphic and sound file can be compressed

   Notes and guidance

   Including the use of run-length encoding (RLE)