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Questions and Answers

What role do parameters play in a procedure?

They provide an interface between the procedure and the program. (correct)

They multiply the execution speed of the code.

They store the results of the procedure.

They define the scope of the procedure.

Which step is NOT part of the procedure execution process?

Return control to the point of origin.

Transfer control to the procedure.

Delete all previous data. (correct)

Perform the desired task.

How can procedures be described in terms of abstraction?

They are specific to one programming language.

They are only needed for large programs.

They simplify programming by hiding the complexity. (correct)

They require all data to be visible at all times.

In RISC-V software, what is the purpose of registers x10–x17?

To pass parameters or return values in procedures. Signup and view all the answers

What is the function of a procedure in programming?

To structure programs for better organization and code reuse. Signup and view all the answers

What is the primary purpose of the jump-and-link instruction in RISC-V?

To branch to an address while saving the address of the next instruction. Signup and view all the answers

In the context of RISC-V assembly language, what does the return address refer to?

The address of the instruction to execute after the procedure finishes. Signup and view all the answers

Which instruction is used to return from a procedure in RISC-V?

jalr x0, 0(x1) Signup and view all the answers

What role does the caller have in the procedure call process?

To provide parameter values and initiate the procedure call. Signup and view all the answers

What is stored in register x1 during a jump-and-link instruction?

The return address for the procedure. Signup and view all the answers

What does the procedure fact return when the parameter n is less than 1?

1 Signup and view all the answers

What is the purpose of the instruction 'addi sp, sp, -8' in the RISC-V assembly code?

To adjust the stack pointer for saving registers Signup and view all the answers

In the context of the fact procedure, what does the instruction 'bge x5, x0, L1' check?

If n is greater than or equal to 0 Signup and view all the answers

What value is stored in register x10 before the procedure fact returns?

The result of the factorial calculation Signup and view all the answers

How does the recursive call to the fact procedure handle the argument n?

It decrements n by 1 Signup and view all the answers

Which register is used to save the return address when entering the fact procedure?

x1 Signup and view all the answers

What happens immediately after the instruction 'addi x10, x0, 1' is executed?

The procedure returns to the caller Signup and view all the answers

What does the instruction 'jal x1, fact' do in the assembly code?

It calls the fact procedure Signup and view all the answers

Before executing the pop instructions, which registers could be loaded back into the original state?

x1 and x10 Signup and view all the answers

How is the value of n modified before the recursive call?

It is decremented by 1 Signup and view all the answers

Study Notes

Procedures in Computer Hardware

Procedures (or functions) are programming tools that improve code readability and reusability.
They enable programmers to focus on individual tasks, using parameters as interfaces for data exchange and result returns.
Procedures implement abstraction in software, acting like self-contained modules that perform tasks without disturbing other parts of the program.
Six steps in procedure execution: parameter placement, control transfer, resource acquisition, task execution, result placement, and control return to the point of origin.

RISC-V Procedure Calling Convention

RISC-V utilizes 32 registers, with x10-x17 dedicated to parameter passing or return values and x1 for storing the return address.
The jal (jump-and-link) instruction branches to a procedure's address and saves the return address in x1.
The return address allows procedures to be called from multiple program locations ensuring successful return.
The jalr (jump-and-link register) instruction uses the address in x1 to return to the calling program.
The calling program (caller) provides parameters in registers x10-x17 and uses jal to branch to the procedure (callee).

Recursive Procedure Example (Factorial Calculation)

A recursive C factorial function is compiled into RISC-V assembly code.
The stack is used to save the return address and the function's argument (n).
Conditional branching occurs based on the value of n. If n < 1, the function returns 1. If n ≥ 1, the argument is decremented and the function calls itself recursively.
The stack is used to manage the nested function calls. The results are returned through register x10.

Stack Allocation in Procedures

Stack allocation is illustrated, considering states before, during, and after a procedure call.
The frame pointer (FP or x8) points to the beginning of the procedure's stack frame, while the stack pointer (SP) points to the top of the stack.
The stack frame accommodates saved registers, return addresses, local variables, and other data.
The frame pointer offers a stable reference point for accessing variables, even as the stack pointer changes.
If no local variables exist on the stack within a procedure, the compiler omits frame pointer setup and restoration to optimize processing speed.

Memory Allocation in RISC-V (Linux)

RISC-V memory is divided into segments: stack, heap, static data segment, text segment, and reserved memory.
The stack grows downwards from high memory addresses.
The text segment (machine code) resides at the start of low memory.
Static data (constants, static variables) is placed above the text segment.
The heap, used for dynamic data structures, is positioned next, growing upwards towards the stack. This arrangement allows efficient memory usage.

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Description

This quiz covers the fundamentals of procedures in computer hardware and the RISC-V procedure calling convention. Learn about the importance of procedures for code readability, reusability, and abstraction. It also explores the register usage for parameter passing in RISC-V.