Questions tagged [pdp-11]

The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years.

The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years. The PDP-11 had several uniquely innovative features, and was easier to program than its predecessors with its use of general registers. Its successor in the mid-range minicomputer niche was the 32-bit VAX-11.

Design features of the PDP-11 influenced the design of microprocessors such as the Motorola 68000; design features of its operating systems, as well as other operating systems from Digital Equipment, influenced the design of other operating systems such as CP/M and hence also MS-DOS. The first officially named version of Unix ran on the PDP-11/20 in 1970. It is commonly stated that the C programming language took advantage of several low-level PDP-11–dependent programming features, albeit not originally by design.

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how does C program transfer arguments under the hood?

This is PDP-11 code mixing C and assembly. In the below, u.u_rsav is an array pointer, savu(u.u_rsav); The assembly code for this function is _savu: bis $340,PS mov (sp)+,r1 mov (sp),r0 …
CCNA
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Encoding/decoding PDP-11 assembly language to binary and hex?

I've been given an assignment where I'm to write the actionPreformed methods for Encode and Decode buttons for an application where a user can hypothetically encode/decode PDP-11 instructions (that are limited to ADD, SUB, MOV[B], CMP[B]). The…
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How many number of bits stored in a memory location in PDP 11

PDP 11 is said to be word addressable which means every data access returns 16 bit data. Suppose I give a read request for address 100 in memory. Will it return 8 bits(LSB) from address 100 and 8bits(MSB) from address 101. And also as PDP 11 has 16…
sandywho
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assembly of pdp-11(simulator)

I have this code on pdp-11 tks = 177560 tkb = 177562 tps = 177564 tpb = 177566 lcs = 177546 . = torg + 2000 main: mov #main, sp mov #kb_int, @#60 mov #200, @#62 mov #101, @#tks mov #clock, @#100 mov #300,…
lego69
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program on Assembly

can somebody please explain what this program is doing? .= torg + 1000 main: mov pc, sp tst –(sp) mov #list1, -(sp) jsr pc, mystery mov r0, res1 tst (sp)+ mov #list2, -(sp) jsr pc,…
lego69
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Ask for explain of some code of UNIX V6

Currently I am reading the book: Lions_Commentary_on_UNIX_6th_Edition, together I am trying to understand the source code of unix v6, and I found some code intriguing: e.g. . = 40^. ... . = 60^. This is some PDP-11 assembly which I am not very good…
wangshuaijie
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how to display DEC floating point format given 32 bits in IEEE standard

I'm currently given 32 bits of data that are in the Digital Equipment Corporation (DEC) floating point format or PDP-11 (or fp-11). The data is given in little endian. In C, how do I get a regular IEEE-754 single precision floating point from…
rob ell
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Understanding Assembly basic code

pointr: .word pointr mov #pointr,r0 mov pointr,r1 Can someone please explain the difference between the values r0 and r1?
Sam12
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printing message in pdp-11

I'm having problem with printing a message in pdp-11. The code is: tks = 177560 tkb = 177562 tps = 177564 tpb = 177566 mask1: .word 177600 WELM: .ascii SOG: mov #0,r2 movb…
shirs
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How to XOR between a byte and a word on PDP-11?

The main problem we encountered is that one number is saved as a byte, the other is saved as a word and we realize that there's a built in XOR in PDP-11.
Sam12
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Meaning of unix v6 assembly code generated by cc compiler?

For example, below is a piece of C code and its assembly code generated by cc compiler. // C code (pre K&R C) foo(a, b) { int c, d; c = a; d = b; return c+d; } // corresponding assembly code generated by cc .global…
user6872780
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i get this message in pdp-11"ODD WORD ADDRESS" what does it mean?

currently working on a code in pdp-11 but i get this error "odd word adress" so i searched in the internet and found this :An odd address error : which occurs if a register used in a word autoincrement or autodecrement instruction becomes odd. and i…
jasmine
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What is the meaning of -(sp) in unix v6 Assembly?

What's the meaning of -(sp)? I am reading code of Unix V6, on PDP-11 the old OS. I already know the meaning of sp, this is stack pointer. Is this same as -1(sp)?
KiYugadgeter
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riddle - replace 4 strokes of code in equivalent 2

tst r0 blt label cmp r0, #11 bgt label As I understand this peace of code is a brench if r0 < 0 or r0 > 11. How can I optimize it to only 2 strokes of code.
KittyT2016
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Addressing Modes in PDP-11 Assembler

I have small question about pdp-11(simulator), I have this command (it begins from the address 1000) add 2500, #2500 and this initial list: register/address - initial value pc 1000 sp 600 2500 3000 and…
lego69
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