Where is Assembly language used to program hardware

assemblyembeddedhardware-programming

I've looked around for a good place to start learning embedded systems design/programming, and while all suggest beginner devices such as Arduino and RaspberryPi, I've never seen any suggestions for programming at the assembly level. I've recently completed my computer science bachelor's, but I've been getting more and more attracted to hardware rather than software programming. I've taken one hardware design course and we did assembly programming for 68k and logic design in Logism. I have a Raspberry Pi, and have messed with it some, but the languages used for these devices are still higher level (C, C++, Python).

So I have a few questions since I'm really interested in lower level design for chips/computer hardware:

What are the applications of Assembly language in today's hardware design? Is it still widely used or is most of it abstracted by higher level languages?

If it is still widely used, what type of jobs involve Assembly programming? What are the most popular platforms for assembly programming (68k, x86, etc.)?

Finally, what are some resources for modern-day Assembly programming, if the above applies?

Thanks, and again I've looked at some of the other questions about diving into embedded systems, so I hope my questions are sufficiently different, but feel free to flag this if my questions were already answered!

Best Answer

What are the applications of Assembly language in today's hardware design? Is it still widely used or is most of it abstracted by higher level languages?

Assembly language is used in specific use cases. It is still the most common in specific use cases in embedded systems software however it is still present in other low level projects like Linux kernel. It is used here and there because there are certain things then can be done only in assembly and because assembly results in a faster and smaller code. I will give you one real life example to make it more clear to you. Some critical parts of firmware for smart cards is written in assembly in order to protect software execution against different types of attacks and assembly is the only language where you fully control binary representation of the program. Compiler might leave security hole in the firmware which might be an entry point for the attacker.

If it is still widely used, what type of jobs involve Assembly programming?

Here you have few example engineering positions requiring advanced assembly language knowledge:

Compiler Engineer.
Firmware Engineer.
Secure Firmware Engineer.
Malware Analyst.

What are the most popular platforms for assembly programming (68k, x86, etc.)?

Check the most popular CPU architectures in these times and you will have the answer (spoiler Intel x86/x64, ARM).

Finally, what are some resources for modern-day Assembly programming, if the above applies?

Google

Related Solutions

How does the stack work in assembly language

I think primarily you're getting confused between a program's stack and any old stack.

A Stack

Is an abstract data structure which consists of information in a Last In First Out system. You put arbitrary objects onto the stack and then you take them off again, much like an in/out tray, the top item is always the one that is taken off and you always put on to the top.

A Programs Stack

Is a stack, it's a section of memory that is used during execution, it generally has a static size per program and frequently used to store function parameters. You push the parameters onto the stack when you call a function and the function either address the stack directly or pops off the variables from the stack.

A programs stack isn't generally hardware (though it's kept in memory so it can be argued as such), but the Stack Pointer which points to a current area of the Stack is generally a CPU register. This makes it a bit more flexible than a LIFO stack as you can change the point at which the stack is addressing.

You should read and make sure you understand the wikipedia article as it gives a good description of the Hardware Stack which is what you are dealing with.

There is also this tutorial which explains the stack in terms of the old 16bit registers but could be helpful and another one specifically about the stack.

From Nils Pipenbrinck:

It's worthy of note that some processors do not implement all of the instructions for accessing and manipulating the stack (push, pop, stack pointer, etc) but the x86 does because of it's frequency of use. In these situations if you wanted a stack you would have to implement it yourself (some MIPS and some ARM processors are created without stacks).

For example, in MIPs a push instruction would be implemented like:

addi $sp, $sp, -4  # Decrement stack pointer by 4  
sw   $t0, ($sp)   # Save $t0 to stack

and a Pop instruction would look like:

lw   $t0, ($sp)   # Copy from stack to $t0  
addi $sp, $sp, 4   # Increment stack pointer by 4

Is assembly the only low level programming language, and if not is it the most widely used

Is the efficiency between a high level language program and a low level one really not even noticeable enough to pay attention to nowadays

Oftentimes, compilers generate a lot better assembly than developers can write. There are certain developers who can beat the compiler. But since writing low-level code requires more attention to details and is harder to write and maintain, it is usually only a small specific pieces of code that get implemented in assembly for efficiency. The difference can be noticeable. But it also can be not-noticable if developers do false-optimizations.

I'd recommend you read Michael Abrash's Graphics Programming Black Book — it has a lot on assembly and optimizations + nice stories from real-life.

and is there another low level language like assembly that is more widely used?

Assembler is probably the lowest level application programming language. The only other resort would be to write binary code by hand, but binary opcodes can hardly be called a "language".

However, programming goes beyond software. Hardware needs to be programmed, too. There are hardware description languages (HDL) that can be used to program hardware (i.e. you can create your own CPU). The most popular HDL languages are Verilog and VHDL.