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Ca65 is an advanced assembler for the 6502, 65C02, and 65816 microprocessors. It is part of the CC65 suite of programming tools, which also includes a compiler and linker. Ca65 supports a wide range of directives for data storage, macros, conditional assembly, and more. It also supports local and global symbols, as well as complex expressions. The assembler is capable of producing object files in O65 format or raw binary files. It is widely used for developing software for retro systems such as the Commodore 64 or Nintendo Entertainment System.

Ask the right questions secure the right Ca65 talent among an increasingly shrinking pool of talent.

First 20 minutes

General Ca65 app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Ca65 application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you define the role of a Ca65 developer?

A Ca65 developer is responsible for writing, testing, and debugging code in the Ca65 assembly language. They also optimize code for performance, maintain documentation, and collaborate with other team members on larger projects.

What are the primary uses of Ca65?

Primarily, Ca65 is used for programming 6502-based microcomputers and video game consoles. It's also used in embedded systems and homebrew game development.

How would you set up a development environment for Ca65?

To set up a development environment for Ca65, you'll need a text editor, the CC65 compiler suite (which includes the Ca65 assembler), and an emulator for the target system.

Describe the difference between absolute and relative addressing in Ca65.

Absolute addressing in Ca65 refers to a specific memory location, whereas relative addressing refers to a location relative to the current program counter.

What are the key features of Ca65?

Key features of Ca65 include support for all 6502, 65C02, and 65816 instructions, a powerful macro language, and support for binary include files and structured programming.

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What you’re looking for early on

Does the candidate have a deep understanding of the Ca65 assembler?

Has the candidate demonstrated problem-solving skills?

Is the candidate able to communicate effectively?

Does the candidate have experience with other relevant technologies?

Next 20 minutes

Specific Ca65 development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you debug a Ca65 program?

Debugging a Ca65 program typically involves using a 6502 debugger or emulator with debugging capabilities. The developer would set breakpoints, step through the code, and inspect memory and registers to identify errors.

What are the benefits of using Ca65 over other assemblers?

Benefits of using Ca65 include its powerful macro language, its support for all 6502 variants, and its integration with the CC65 compiler suite, making it easier to mix assembly and C code.

Describe the difference between JMP and JSR in Ca65.

In Ca65, JMP (Jump) is used to change the program counter to a new location, while JSR (Jump to SubRoutine) is used to call a subroutine, saving the return address on the stack.

How would you optimize code in Ca65?

Optimizing code in Ca65 involves strategies like minimizing memory usage, reducing the number of instructions, and taking advantage of the 6502's unique instruction set and addressing modes.

What are the challenges of programming in Ca65 and how would you overcome them?

Challenges of programming in Ca65 include the complexity of assembly language and the limited resources of 6502-based systems. Overcoming these challenges requires a deep understanding of the 6502 architecture and careful planning and optimization.

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At this point, a skilled Ca65 engineer should demonstrate strong problem-solving abilities, proficiency in Ca65 programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Ca65.

What does this simple piece of CA65 assembly code do?
LDA #$00
STA $0200
This code loads the accumulator with the value 0 (LDA #$00), then stores the value in the accumulator to the memory address $0200 (STA $0200).
What will be the output of this CA65 assembly code?
LDA #$01
BEQ skip
LDA #$02
skip: STA $0200
The output will be 2. The code loads the accumulator with the value 1, then checks if it is equal to zero. If it is, it skips the next instruction. Since it is not, it loads the accumulator with the value 2, then stores that value in the memory address $0200.
What does this CA65 assembly code do, which manipulates an array of data?
LDX #$00
loop: LDA array,X
STA $0200,X
INX
CPX #$10
BNE loop
This code copies the first 16 bytes of data from an array to the memory addresses starting at $0200. It uses the X register as an index to loop through the array.
What does this CA65 assembly code do, which uses the IRQ interrupt?
SEI
LDA #$34
STA $FFFE
CLI
This code sets the IRQ interrupt vector to the address $0034. It first disables interrupts (SEI), then stores the low byte of the address to the interrupt vector ($FFFE), and finally re-enables interrupts (CLI).

Wrap-up questions

Final candidate for Ca65 Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Ca65 application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you handle a large project in Ca65?

Handling a large project in Ca65 would involve breaking the project down into smaller, manageable components, making extensive use of subroutines and macros, and maintaining thorough documentation.

Describe the difference between zero page and absolute addressing in Ca65.

In Ca65, zero page addressing refers to the first 256 bytes of memory, which can be accessed more quickly and with shorter instructions than other memory locations. Absolute addressing can refer to any location in memory.

What are the best practices for writing clean and maintainable code in Ca65?

Best practices for writing clean and maintainable code in Ca65 include using meaningful labels and comments, following a consistent coding style, and making use of subroutines and macros to avoid repeating code.

Ca65 application related

Product Perfect's Ca65 development capabilities

Beyond hiring for your Ca65 engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Ca65 projects, and can engage in multiple capacities.

Ca65 Consultive assessments

Ca65 Application Conversion Assessment Ca65 Application Integration Assessment Ca65 Data & Database Integration Assessment

Custom Ca65 development projects

Custom Ca65 App Conversion Ca65 Custom App Development Process App UI Design for Ca65 Facelifts

Hiring guide for Ca65 Engineers

Ca65 Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Ca65 engineer at this point.

Ca65 Consultive assessments

Custom Ca65 development projects