A451 Written Exam
OCR Computing GCSE unit A451 is a written exam of 1 hour and 30 minutes. It consist of the following main topics
1) Fundamentals of Computer Systems :
This topic introduces computer systems and provides a foundation for the remaining topics of the unit. Candidates should develop a mental model of a computer system which comprises hardware and software and in which data are input and processed, data may be stored and results from the processing are output.
Candidates should be able to define a computer system, describe the importance of computer systems in the modern world, explain the need for reliability in computer systems, and explain the importance of ethical, environmental and legal considerations when creating computer systems.
2) Computer Hardware :
Candidates should be able to define the term hardware and have an understanding of the CPU, binary logic, memory (RAM and ROM), input and output devices and secondary storage.
3) Computer Software :
Candidates should be able to define the term software and have an understanding of operating systems functions such as user interface, memory management, multi-tasking and security; describe the purpose and use of common utility programs, disk organisation and system maintenance. They should also be able to discuss the relative merits of custom written, off-the-shelf, open source and proprietary software.
4) Representation of data in computer systems :
Candidates should be able to define the terms: bit, nibble, byte, kilobyte, megabyte and terabyte. That should understand that data needs to be converted into binary format to be processed by a computer. They should be able to: convert positive denary whole numbers (0-255) into 8-bit binary numbers and vice versa; add two 8-bit binary integers and explain overflow errors that might occur; convert positive denary whole numbers (0-255) into 2-digit hexadecimal numbers and vice versa; explain the use of hexadecimal numbers to represent binary numbers.
They should be able to explain how instructions are coded as bit patterns and how a computer distinguishes between instructions and data.
For characters, they should be able to explain the use of binary codes to represent characters; explain the term character set and describe the relationship between the number of bits per character and the number of characters which can be represented.
For images, they should be able to explain the representation of an image as a series of pixels represented in binary; explain the need for metadata; discuss the effect of colour depth and resolution on the size of an image file.
For sounds, they should be able to explain how sound can be sampled and stored in digital form and explain how sampling intervals and other considerations affect the size of a sound file and quality of playback.
5) Databases :
Candidates should be able to describe a database as a persistent organised store of data and explain the use of data handing software to create, maintain and interrogate databases. They should be able to describe how a DBMS allows separation of data from applications and why this is desirable.
For relational databases, they should be able to understand the relationship between entities and tables; understand the components of a relational database such as tables, forms, queries and reports; understand the use of logical operators; explain the use of key fields and describe methods of validating data as it is input.
6) Computer Communications and Networking :
Candidates should be able to explain the advantages of networking stand-alone computers into a local area network; describe the hardware needed to create such a local area network; explain the different roles of computers in client-server and peer-to-peer networks; describe common LAN topologies; explain the difference between a LAN and a WAN; explain the terms IP addressing, MAC addressing, packets and protocols; explain the need for network security; describe and justify network policies such as acceptable use, disaster recovery, failover, backup and archiving.
For the internet, they should be able to describe its nature as a worldwide collection of computer networks; describe the hardware needed to connect to the internet; explain the need for IP addressing of resources; describe common file standards such as JPG, GIF, PDF, MP3; explain the importance of compression and describe the differences between lossy and lossless compression.
7) Programming :
Candidates should be able to understand algorithms (written in pseudo-code or flow diagram), explain what they do and correct or complete them; they should be able to produce their own pseudo-code or flow diagrams to solve problems.
They should be able to explain the difference between high-level code and machine code; explain the need for translators to convert high-level code to machine code; describe the characteristics of an assembler, compiler and an interpreter; describe the common tools and facilities available in an integrated development environment.
They should understand and use sequence in an algorithm; understand and use selection in an algorithm (IF and CASE); understand and use iteration in an algorithm (FOR, WHILE and REPEAT).
Candidates should be able to: define the terms variable and constant as used in an imperative language; use variables and constants; describe the data types: integer, real, Boolean, character and string; select and justify appropriate data types for a given program; perform common operations on numeric and Boolean data; use one-dimensional arrays.
Finally, Candidates should be able to: describe syntax errors and logic errors which may occur while developing a program; understand and identify syntax and logic errors; select and justify test data for a program, stating the expected outcome of each test.
OCR Computing GCSE unit A451 is a written exam of 1 hour and 30 minutes. It consist of the following main topics
1) Fundamentals of Computer Systems :
This topic introduces computer systems and provides a foundation for the remaining topics of the unit. Candidates should develop a mental model of a computer system which comprises hardware and software and in which data are input and processed, data may be stored and results from the processing are output.
Candidates should be able to define a computer system, describe the importance of computer systems in the modern world, explain the need for reliability in computer systems, and explain the importance of ethical, environmental and legal considerations when creating computer systems.
2) Computer Hardware :
Candidates should be able to define the term hardware and have an understanding of the CPU, binary logic, memory (RAM and ROM), input and output devices and secondary storage.
3) Computer Software :
Candidates should be able to define the term software and have an understanding of operating systems functions such as user interface, memory management, multi-tasking and security; describe the purpose and use of common utility programs, disk organisation and system maintenance. They should also be able to discuss the relative merits of custom written, off-the-shelf, open source and proprietary software.
4) Representation of data in computer systems :
Candidates should be able to define the terms: bit, nibble, byte, kilobyte, megabyte and terabyte. That should understand that data needs to be converted into binary format to be processed by a computer. They should be able to: convert positive denary whole numbers (0-255) into 8-bit binary numbers and vice versa; add two 8-bit binary integers and explain overflow errors that might occur; convert positive denary whole numbers (0-255) into 2-digit hexadecimal numbers and vice versa; explain the use of hexadecimal numbers to represent binary numbers.
They should be able to explain how instructions are coded as bit patterns and how a computer distinguishes between instructions and data.
For characters, they should be able to explain the use of binary codes to represent characters; explain the term character set and describe the relationship between the number of bits per character and the number of characters which can be represented.
For images, they should be able to explain the representation of an image as a series of pixels represented in binary; explain the need for metadata; discuss the effect of colour depth and resolution on the size of an image file.
For sounds, they should be able to explain how sound can be sampled and stored in digital form and explain how sampling intervals and other considerations affect the size of a sound file and quality of playback.
5) Databases :
Candidates should be able to describe a database as a persistent organised store of data and explain the use of data handing software to create, maintain and interrogate databases. They should be able to describe how a DBMS allows separation of data from applications and why this is desirable.
For relational databases, they should be able to understand the relationship between entities and tables; understand the components of a relational database such as tables, forms, queries and reports; understand the use of logical operators; explain the use of key fields and describe methods of validating data as it is input.
6) Computer Communications and Networking :
Candidates should be able to explain the advantages of networking stand-alone computers into a local area network; describe the hardware needed to create such a local area network; explain the different roles of computers in client-server and peer-to-peer networks; describe common LAN topologies; explain the difference between a LAN and a WAN; explain the terms IP addressing, MAC addressing, packets and protocols; explain the need for network security; describe and justify network policies such as acceptable use, disaster recovery, failover, backup and archiving.
For the internet, they should be able to describe its nature as a worldwide collection of computer networks; describe the hardware needed to connect to the internet; explain the need for IP addressing of resources; describe common file standards such as JPG, GIF, PDF, MP3; explain the importance of compression and describe the differences between lossy and lossless compression.
7) Programming :
Candidates should be able to understand algorithms (written in pseudo-code or flow diagram), explain what they do and correct or complete them; they should be able to produce their own pseudo-code or flow diagrams to solve problems.
They should be able to explain the difference between high-level code and machine code; explain the need for translators to convert high-level code to machine code; describe the characteristics of an assembler, compiler and an interpreter; describe the common tools and facilities available in an integrated development environment.
They should understand and use sequence in an algorithm; understand and use selection in an algorithm (IF and CASE); understand and use iteration in an algorithm (FOR, WHILE and REPEAT).
Candidates should be able to: define the terms variable and constant as used in an imperative language; use variables and constants; describe the data types: integer, real, Boolean, character and string; select and justify appropriate data types for a given program; perform common operations on numeric and Boolean data; use one-dimensional arrays.
Finally, Candidates should be able to: describe syntax errors and logic errors which may occur while developing a program; understand and identify syntax and logic errors; select and justify test data for a program, stating the expected outcome of each test.