ocr GCSE Computer Science J277/02 Question Paper and
Mark Scheme June2023.
Analogue sound signals are... - ansContinuous.
Cache Size - ansA part of the main store between the central processor and the rest of the memory. It
has extremely fast access, so sections of a program and its associated data are copied there to take
advantage of its short fetch cycle. The larger the size of the cache the more that can be copied and stored
here without having to go back to slower main memory (RAM), this has a significant impact on the speed
of processing. There are 3 levels of cache, 1 being the fastest but smallest, and 3 being the slowest but
the biggest.
Characteristics of storage - anscapacity, speed, portability, durability, reliability and cost
Clock Speed - ansdictates how many instructions the CPU can process each second, for example,
3.2GHz means 3.2 billion cycles per second.
Digital sound signals are... - ansDiscrete.
How do you work out file size? (bits) - anssample rate x bit depth x duration
How do you work out the bits per pixel? (For example 16 colours) - ans2 to the power of something. (For
example 2 to the power of 4 = 16)
How does the CPU work? - ansThe PC holds the address of the next instruction. It gets sent to the MAR,
then to the MDR, decoded by the CU, executed by the ALU, and stored temporarily in the ACC.
How many bits is extended ASCII? - ansExtended ASCII is 8 bits.
How many bits is standard ASCII? - ansStandard ASCII is 7 bits.
How many bits is Unicode? - ansUnicode is 16 bits.
Number of Cores - ansThe number of duplicate processors linked together on a single chip
RAM and ROM - ansTwo types of memory. RAM (Random Access Memory) is the main memory used
while the PC is working. RAM is temporary. ROM (Read Only Memory) is for information needed by the
PC and cannot be changed. RAM is volatile and the data is deleted when power is lost, and ROM is non-
volatile, which means data is kept on it when power is lost.
Recording quality improves when... - ansThe more frequently we sample the sound, and the more
accurately we record the wave height.
Sound is sampled using... - ansBit Depth and Sample Rate
What are bitmaps made up of? - ansPICture ELements, or pixels.
What are the benefits of compressing files? - ansSmaller files = fewer packets = faster transmission time.
Quicker to complete transmission.
Reduces download time.
What are the Main Components of a Computer? - ansInput/Output Devices, Main Memory and Secondary
Storage and the CPU.
What are the registers in the CPU? - ansProgram Counter (PC), Memory Address Register (MAR),
Memory Data Register (MDR) and Accumulator.
