11/3/71 AS (I) NAME as -- assembler SYNOPSIS as name1 . . . DESCRIPTION as assembles the concatenation of name1, .... as is based on the DEC--provided assembler PAL--11R [references], although it was coded locally. Therefore, only the differences will be recorded. Character changes are: for use @ * # $ ; / In as, the character ";" is a logical new line; several operations may appear on one line if separated by ";". Several new expression operators have been provided: \> right shift (logical) \< left shift * multiplication \/ division % remainder (no longer means "register") ! one's complement [] parentheses for grouping ^ result has value of left, type of right For example location 0 (relocatable) can be written "0^."; another way to denote register 2 is "2^r0" All of the preceding operators are binary; if a left operand is missing, it is taken to be 0. The ! operator adds its left operand to the one's complement of its right operand. There is a conditional assembly operation code different from that of PAL-11R (whose conditionals are not provided): .if expression ... .end if If the expression evaluates to non-zero the section of code between the ".if" and the .endif is assembled; otherwise it is ignored. ".if" s may be nested. Temporary labels like those introduced by Knuth [reference] may be employed. A temporary label is defined as follows: 11/3/71 AS (I) n: where n is a digit 0 ,.. 9. Symbols of the form "nf" refer to the first label n: following the use of the symbol; those of the form nb refer to the last "n:". The same n may be used many times. Labels of this form are less taxing both on the imagination of the programmer and on the symbol table space of the assembler. The PAL-11R opcodes ".eot" and ".end" are redundant and are omitted. The symbols r0 ... r5 sp pc ac mq div mul lsh ash nor csw are redefined with appropriate values. The symbol csw refers to the console switches. ".." is the relocation constant and is added to each relocatable symbol; normally it is 40000(8); it may be changed to assemble a section of code at a location different from that in which it will be executed. It is illegal to assign a value to "."less than its current value. The new opcode "sys" is used to specify system calls. Names for system calls are predefined. See the section on system calls for their names. Strings of characters may be assembled in a way more convenient than PAL-11's ".ascii" operation (which is, therefore, omitted). Strings are included between the string quotes '<' and '>' : <here is a string> Escape sequences exist to enter non graphic and other difficult characters. These sequences are also effective in single and double character constants introduced by single (') and double (") quotes respectively. 11/3/71 AS (I) use for \n newline (012) \0 NULL (000) \> > \t TAB (011) \\ \ The binary output of the assembler is placed on the file a.out in the current directory. a.out also contains the symbol table from the assembly and relocation bits. The output of the assembler is executable immediately if the assembly was error--free and if there were no unresolved external references. The link editor ld may be used to combine several assembly outputs and resolve global symbols. The multiple location counter feature of PALIIR is not supported. The assembler does not produce a listing of the source program. This is not a serious drawback; the debugger db discussed below is sufficiently powerful to render a printed octal translation of the source unnecessary. FILES /etc/as2 pass 2 of the assembler a.tmpl temporary a.tmp2 temporary a.tmp3 temporary a.out object SEE ALSO ld, nm, sh, un, db, a.out (format of output) DIAGNOSTICS When an input file cannot be read, its name followed by a question mark is typed and assembly ceases. When syntactic or semantic errors occur, a single--character diagnostic is typed out together with the line number and the file name in which it occurred. Errors in pass I cause cancellation of pass 2. The possible errors are: ) parentheses error ] parentheses error * Indirection ("*") used illegally A error in Address B Branch instruction has too remote an address E error in Expression F error in local ( or "b") type symbol G Garbage (unknown) character M Multiply defined symbol as label 0 Odd---- word quantity assembled at odd 11/3/71 AS (I) address P Phase error " .." different in pass 2 from pass 1 value R Relocation error U Undefined symbol X syntaX error BUGS Symbol table overflow is not checked. OWNER dmr