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Questions and Answers
What value should EBX hold after the first function call if it starts from zero?
What value should EBX hold after the first function call if it starts from zero?
What differs a call instruction from a simple unconditional branch?
What differs a call instruction from a simple unconditional branch?
During the execution of an instruction, what happens to the instruction pointer (EIP) when fetching and decoding occurs?
During the execution of an instruction, what happens to the instruction pointer (EIP) when fetching and decoding occurs?
What is the value of EAX expected to be after a function call where it is incremented by 3?
What is the value of EAX expected to be after a function call where it is incremented by 3?
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What happens at the decode stage of instruction processing in terms of memory addressing?
What happens at the decode stage of instruction processing in terms of memory addressing?
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What is the primary purpose of using XOR Ax, Ax in assembly language?
What is the primary purpose of using XOR Ax, Ax in assembly language?
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Which logical operation mentioned cannot be used to clear a register?
Which logical operation mentioned cannot be used to clear a register?
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Which registers are primarily involved in the multiplication operation as described?
Which registers are primarily involved in the multiplication operation as described?
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What happens to the higher-order result when multiplying two 16-bit numbers?
What happens to the higher-order result when multiplying two 16-bit numbers?
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What is the effect of the MOV instruction in assembly language?
What is the effect of the MOV instruction in assembly language?
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Which of the following logical operations is used for inverting a register's value?
Which of the following logical operations is used for inverting a register's value?
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When performing multiplication in assembly, what must be done before executing the operation?
When performing multiplication in assembly, what must be done before executing the operation?
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What is the outcome of executing an XOR instruction with a register and itself in terms of processor flags?
What is the outcome of executing an XOR instruction with a register and itself in terms of processor flags?
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In assembly language, which operation is indicated when you need to increase the value of a register?
In assembly language, which operation is indicated when you need to increase the value of a register?
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Which of the following is NOT a characteristic of the assembly language instructions discussed?
Which of the following is NOT a characteristic of the assembly language instructions discussed?
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What is the fundamental difference between high-level languages and assembly language?
What is the fundamental difference between high-level languages and assembly language?
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What is meant by 'immediate addressing' in assembly language?
What is meant by 'immediate addressing' in assembly language?
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In which addressing mode is the address value located within a register?
In which addressing mode is the address value located within a register?
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What happens when executing the instruction 'MOV Ax, 0x40'?
What happens when executing the instruction 'MOV Ax, 0x40'?
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What is direct addressing in assembly language?
What is direct addressing in assembly language?
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What does the instruction 'MOV Ax, [Bx]' do?
What does the instruction 'MOV Ax, [Bx]' do?
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When dealing with logical addresses, what data size is typically focused on?
When dealing with logical addresses, what data size is typically focused on?
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What does the term 'DWORD' represent in the context of microprocessor data access?
What does the term 'DWORD' represent in the context of microprocessor data access?
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When executing the command 'MOV Bx, word pointer Cx', what type of data is being accessed?
When executing the command 'MOV Bx, word pointer Cx', what type of data is being accessed?
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What is the purpose of a segment register in the context of accessing memory data?
What is the purpose of a segment register in the context of accessing memory data?
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If the instruction 'MOV EAx, DWORD pointer Bx' is executed, what does this imply about the data being loaded?
If the instruction 'MOV EAx, DWORD pointer Bx' is executed, what does this imply about the data being loaded?
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What would happen if a variable's address in Cx is accessed with an incorrect pointer size in the MOV instruction?
What would happen if a variable's address in Cx is accessed with an incorrect pointer size in the MOV instruction?
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What register must typically be used in conjunction with general-purpose registers when accessing memory in this context?
What register must typically be used in conjunction with general-purpose registers when accessing memory in this context?
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If the Cx register contains the value 0x1000, how many bytes will be accessed when using 'MOV Bx, word pointer Cx'?
If the Cx register contains the value 0x1000, how many bytes will be accessed when using 'MOV Bx, word pointer Cx'?
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What does 'MOV Bx, word pointer Cx' imply about the action on the data at the specified address?
What does 'MOV Bx, word pointer Cx' imply about the action on the data at the specified address?
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What happens when using a 'DWORD pointer' with insufficient register size to store the data?
What happens when using a 'DWORD pointer' with insufficient register size to store the data?
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What occurs to the stack pointer when executing a PUSH instruction involving an 8-bit register?
What occurs to the stack pointer when executing a PUSH instruction involving an 8-bit register?
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How many bytes are decremented from the stack pointer when executing PUSH EAX?
How many bytes are decremented from the stack pointer when executing PUSH EAX?
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What is the result of executing PUSH CX after a previous PUSH EBX operation?
What is the result of executing PUSH CX after a previous PUSH EBX operation?
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What is the purpose of the POP operation in relation to the stack?
What is the purpose of the POP operation in relation to the stack?
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When executing a series of PUSH instructions, how does the stack segment behave?
When executing a series of PUSH instructions, how does the stack segment behave?
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How many locations in memory are used when PUSH EBX is executed if EBX is 32 bits?
How many locations in memory are used when PUSH EBX is executed if EBX is 32 bits?
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What happens to the contents of the registers during multiple PUSH operations?
What happens to the contents of the registers during multiple PUSH operations?
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In the logical memory map, how is data accessed?
In the logical memory map, how is data accessed?
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What is indicated by the stack pointer addressing during PUSH operations?
What is indicated by the stack pointer addressing during PUSH operations?
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Which instruction would decrease the stack pointer by 2 bytes when executed?
Which instruction would decrease the stack pointer by 2 bytes when executed?
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Study Notes
C Programming and Assembly Language Notes
- The course covers C programming and assembly language, bridging the gap between high-level and low-level languages.
- Students often lack a physical understanding of how C programs execute in microprocessors.
- Course objectives include translating function calls to assembly, explaining parameter passing, and local variable storage on the stack.
- Demonstrating how local variable space is allocated by a compiler, explaining what happens when local variables go out of scope after a function call, listing out the instructions needed before and after function entry.
- Students will learn different calling conventions for C functions and the subtle differences between C and C++ at the assembly level.
- Exploiting particular hardware instructions to accelerate C functions and understanding why recursion might not be the optimal performance choice.
- Students will be comfortable with the references "The C Programming Language" by Kernighan and Ritchie second edition, and "The INTEL Microprocessors - Architecture, Programming and Interfacing" by Barry B. Brey 8th edition.
- C programming proficiency, and working knowledge assembly language programming.
Week 1 (Lecture 1-6)
- Introduction of the 8086 processor architecture
- Description of commonly used assembly instructions
- Understanding the stack and related instructions
- Introduction to Call and Return instructions
Week 2 (Lecture 7-11)
- Detailed explanation of C programming and inline assembly
- Exploration of data types and their sizes (e.g. byte, word, double word)
- Specific examples of inline assembly, covering ALU operations, string length, and multiplication with repeated addition
- Implementing operations to swap variables using both C and inline assembly.
Week 3 (Lecture 12-16)
- Compilation steps in C programming
- Translating high-level function calls to low-level assembly instructions
- Introduction to prologue and epilogue
- Explanation of calling conventions
- Explanation of how variables are passed.
- C vs. C++ assembly-level comparison and optimization of C functions using hardware loops: memcpy and strlen.
- Recursion analysis and comparisons with software loops.
Week 4 (Lecture 17-20)
- Detailed discussion of references and prerequisites, focusing on the Intel microprocessor architecture.
- Discussion regarding how the compiler translates high-level C/C++ code into low-level machine instructions and how the compiler handles variable argument Lists passing.
- Explanation and analysis of code and operations with variable argument lists, like printf.
- Overview of the compiler's pre-compilation, compilation, and linking phases.
- Emphasis on the importance of the main function and its role in program execution and linking process.
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