Now uses -ms macros

doc/em/ispace.nr

@@ -1,6 +1,5 @@
-.SN 3
-.BP
-.S1 "INSTRUCTION ADDRESS SPACE"
+.bp
+.P1 "INSTRUCTION ADDRESS SPACE"
 The instruction space of the EM machine contains
 the code for procedures.
 Tables necessary for the execution of this code, for example, procedure
@@ -10,14 +9,14 @@ the execution of a program, so that it may be
 protected.
 No further restrictions to the instruction address space are
 necessary for the abstract and assembly language level.
-.P
+.PP
 Each procedure has a single entry point: the first instruction.
 A special type of pointer identifies a procedure.
 Pointers into the instruction
 address space have the same size as pointers into data space and
 can, for example, contain the address of the first instruction
 or an index in a procedure descriptor table.
-.A
+.QQ
 There is a single EM program counter, PC, pointing
 to the next instruction to be executed.
 The procedure pointed to by PC is
@@ -28,35 +27,31 @@ The calling procedure remains 'active' and is resumed whenever the called
 procedure returns.
 Note that a procedure has several 'active' invocations when
 called recursively.
-.P
+.PP
 Each procedure must return properly.
 It is not allowed to fall through to the
 code of the next procedure.
 There are several ways to exit from a procedure:
-.IS 3
-.PS
-.PT
+.IP -
 the RET instruction, which returns to the
 calling procedure.
-.PT
+.IP -
 the RTT instruction, which exits a trap handling routine and resumes
 the trapping instruction (see next chapter).
-.PT
+.IP -
 the GTO instruction, which is used for non-local goto's.
 It can remove several frames from the stack and transfer
 control to an active procedure.
 (see also MES~11 in paragraph 11.1.4.4)
-.PE
-.IE
-.P
+.PP
 All branch instructions can transfer control
 to any label within the same procedure.
 Branch instructions can never jump out of a procedure.
-.P
+.PP
 Several language implementations use a so called procedure
 instance identifier, a combination of a procedure identifier and
 the LB of a stack frame, also called static link.
-.P
+.PP
 The program text for each procedure, as well as any tables,
 are fragments and can be allocated anywhere
 in the instruction address space.