Page 63 - Computer_Science_F5

Computer Science Registers the outcome of recent operations,
such as carry flags or zero flags,
In the heart of a computer processor lies a
used for conditional branching and
critical set of high-speed memory locations
error handling.
called registers. Registers act as the CPU’s
workbench, temporarily storing data that
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is actively involved in calculations or
registers
manipulations. Their close proximity to Function and operations of CPU
the processor allows for significantly faster (a) Data storage and
access compared to fetching data from manipulation: Registers act as a
cache and main memory. temporary holding ground for data
being processed. Instructions in
Classification of registers: the ISA typically reference specific
There are two main classifications of registers for operands (data involved
registers within an ISA, each with distinct in the operation) and destinations for
purposes: the results.
(b) Improving performance: By keeping
(a) General Purpose Registers (GPRs): frequently accessed data readily
These are versatile storage locations available, registers significantly
that can be used by any instruction in reduce the need to fetch data from
the CPU. They can store a variety of slower main memory, leading to faster
data types like integers, floating-point execution speeds.
numbers, or memory addresses during (c) Facilitating function calls: When a
program execution. program calls a function, arguments
are often passed through registers,
(b) Special Purpose Registers (SPRs): enabling efficient communication
These registers are dedicated to specific between different parts of the code.
control functions for the CPU itself. (d) Conditional branching: Status flags
They hold vital information for smooth set in special purpose registers are
operation. Examples are; used for conditional branching in
(i) Program Counter (PC): This register programs.
keeps track of the next instruction to
be executed, ensuring that program Visualizing registers
flows seamlessly. As depicted in Figure 1.52, a processor

(ii) Stack Pointer (SP): This register houses multiple register files such
plays an important role in managing as GPRs, and SPRs. Data paths,
function calls and local variables illustrated in the form of arrows, show
within a program. how data flows between registers, and
(iii) Status Registers (SR): These the Arithmetic Logic Unit (ALU) for
registers hold information about performing calculations, and the main

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for Advanced Secondary Schools

Computer Science Form 5.indd 54 23/07/2024 12:32