Frequently asked questions on Pass 1:

The program name does not have to be compared or used. We are using the filename as the "base" name for the output files. Yes, it would be an error if it is missing, since the specs say that it should be there.

Yes, a constant can be used anywhere that a literal can be used. All numeric constants must be HALF, Pass 2 will pad with zeros to fill the 26-bit space in EXIT.

Since the intermediate file is used by the programmer for debugging, comments should be copied from the source file to the intermediate.

Spacing in the intermediate file is important for two reasons:
• human readability for debugging
• machine readability for input into Pass 2
So, it doesn't have to be perfect, but anywhere that there is at least one space between items in the input, there should be at least one space in the output. That makes the intermediate file work for both purposes.

Although the specs say that the assembler is case insensitive, our input test files will all be upper case, except in comments and inside strings. So, you don't have to up-case anything to do comparisons. If you want to up-case comments, that's OK, but don't change lower case characters in constant strings to upper case.

Yes (that's in the pass1 assignment doc) and absolutely yes, Olympus will core dump if you try to read from a NULL file pointer. You should also check for failure when you open a file for output.

It should, but it's always safe to use isspace() where possible. Be careful when using strtok in .CONST since constant strings can contain \t and spaces.

The assignment doesn't tell how to handle code and data counters and addresses when errors are found. That's because I don't care and won't worry about that when we grade on the invalid input file. All that matters there is that you find as many errors as possible. It's hard enough to get pass1 to work on valid code and to find errors at all, I don't expect your program to behave in a certain way when errors are found, except to print the error message. However, if you don't have enough to do, I can provide detailed specifications on exactly how to handle every possible error condition...

The short answer is that you are programming in C, core dumps are a fact of life.
The long answer is that you are most likely trying to do something with a NULL string. You can't use any string functions (strcpy, strcmp, strtok) or fprintf with a NULL string. Always check to see if the result of a strtok is NULL before doing anything with it. (I assume, of course that you haven't forgotten that pesky & again...)

Forget about it, I changed my mind...
Actually, you can only do very limited range checking on constants since you don't know what they will be used for until pass 2. The same constant could be used as an unsigned number or as a signed number or as an EXIT code or etc. and all of those uses have different valid ranges.
So, don't bother to check the size of numeric constants in pass 1, just make sure that they are either decimal, hexadecimal (%) or binary (^).

This is easy. Names can't be duplicates, opcode names or directives. The only valid data types we have are DEFW, DEFH, DEFB or DEFX. Then, the 3rd column must have only a decimal number or a numeric constant (can't use strings or single characters here). You will have to look the constant names up in the symbol table and check their type, but that's the hardest part of the .DATA section.

You need to check for:
• labels that end in a : and aren't duplicate symbols
• is it a valid opcode
• the correct number of operands for that opcode
• the correct type of operands for that opcode:
  registers where registers go, some valid identifier where labels or data variables go (you can't check for whether they have been defined, because of possible forward references, so don't bother) and either a constant or valid numeric or single character literal where immediate values can go.
Don't check the values of constants. Only look constant names up in the symbol table to see if they have been defined, don't look up labels or data variables.

Of course you should worry about them, you should stay up all night worrying about the poor lost or damaged .DIRECTIVEs... Oh, you're already staying up all night working on this assignment, well then... nevermind...

In order to make life easier for everyone, we won't have any invalid, missing or misspelled .DIRECTIVEs in our test programs. We also won't have any extra .DIRECTIVEs or have them out of order (.PROGRAM, then .CONST, then [.DATA | .CODE | .EXTERN], then .END, as specified).

• Make sure that you are in the directory where you have your pass1.c, pass2.c and assembler.h files.
• at the Olympus prompt, type make submit
• if there are no errors shown, your files were submitted
• only the three files listed above were submitted, if you modified any other files they won't be included when we grade