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Simpler "Hello World" Demonstrated In C
An anonymous reader writes "Wondering where all that bloat comes from, causing even the classic 'Hello world' to weigh in at 11 KB? An MIT programmer decided to make a Linux C program so simple, she could explain every byte of the assembly. She found that gcc was including libc even when you don't ask for it. The blog shows how to compile a much simpler 'Hello world,' using no libraries at all. This takes me back to the days of programming bare-metal on DOS!"
Mainframers have been using this most simple of all utilities for decades - literally. The Wikipedia entry on it has a good write-up about this (literal) do-nothing program. It's whole purpose is to provide a mechanisim to to exploit the various functions contained in JCL to create, delete, and otherwise manipulate datasets on mainframes.
The wikipedia entry is here: http://en.wikipedia.org/wiki/IEFBR14
Ken
char*_="Hello world.\n";
That is it - the whole program.
I have mod points and I am not afraid to use them
"An 11k app is not going to make me, or my computer, say 'Good Bye World'"
It is if your computer is a 38-cent Atmel AVR tiny 10, which only has enough space for 512 12-bit instruction words. This chip is about half the size of a sunflower seed, but is faster, and, in several ways, more powerful, than the original $5000 IBM PC from 1981.
Get away from the idea of Gigahertz desktops and $1000 laptops and join the real computer revolution!
For me, if it costs more that $5, it's not a computer that I take seriously. It's just a 20th-century digital processing appliance.
It was uploaded to Reddit 12 hours ago; that's probably why it's just reaching Slashdot now.
Parent said a lot of words...
But missed the point: http://www2.latech.edu/~acm/helloworld/c.html
"This program is (supposedly) the smallest C program able to print "Hello world.". The compilation itself produces the desired printout and the program need not be actually run."
This author takes full ownership and responsibility for the unpopular opinions outlined above.
#hello world tiny program
.data
.text
.equ SYSCALL, 0x80
.equ SYS_EXIT, 1
.equ SYS_WRITE, 4
.equ STDOUT, 1
.section
hello:
.ascii "hello world!\n"
.section
.globl _start
_start:
movb $SYS_WRITE, %al #put write syscall in eax
movb $STDOUT, %bl #set stream to stdout
movl $hello, %ecx #give address of start of buffer to print
movb $13, %dl #how many characters of buffer to print
int $SYSCALL
movb $SYS_EXIT, %al
int $SYSCALL
The above is a tiny hello world program i wrote myself, it's worth noting that even the resulting binary is larger than it needs to be, I wound up with a 133 byte binary by moving the text string into the ELF header via hex editor, and changing the instruction data to point to the new addresses.
Kind of hard to get it smaller than that while keeping it in ELF format, considering the actual object code in the binary was something like 15 bytes with the data illegally in the header.
c:\ xxx>debug :001D
-a
mov dx, 100
mov cx, 000D
mov bx, 1
mov ah, 40
int 21
mov ah, 4C
int 21
-f 111 "Hello World!"
-a100
mov dx, 0111
-r cx
-n c:\ xxx\ hello.com
-w
-q
c:\ xxx>hello.com
Hello World!
c:\ xxx>dir hello.com
03/18/2011 11:29 AM 29 HELLO.COM
Back in the early 1980s, I was doing development on MS-DOS 2.11 - the first real working version of MS-DOS that resembled Xenix more than CP/M.
I was using a combination of Lattice C and assembly language to do my day job. But I was upset about the libc bloat that Lattice C would drag into the program. Over the Christmas break, I sat down and wrote a tiny version of libc, with the 60% of the calls I actually used. Most of them were either thin wrappers on top of MS-DOS Int21 calls, assembly language implementations (the string functions), or reduced functionality (printf didn't handle strange alignments, floats or doubles), and custom startup/exit code. I also structured the library so that the linker would only link in functions that were actually used. For simple executables, I saw the on-disk file size drop from 10KB-20KB down to 400-600 bytes. Another thing that reduced on-disk file size was to create .com programs, rather than .exe programs.
I was also writing the handful of unix commands that I couldn't do without (ls, cat, cut, paste, grep, fgrep, etc). Since I was implementing dozens of Unix commands, each statically linked to libc, it was very important to reduce the over-all size of each executable. Most of the smaller trivial commands were less than 1KB in size. I think the largest was 4KB. I also had an emacs clone* that was 36KB when compiled and linked against my tiny lib.
For the longest time, I carried around a bootable MS-DOS 2.11 floppy, with my dozens of Unix commands, an emacs-like editor, Lattice C compiler, tiny libc, and some core MS-DOS programs. It allowed my to have my entire development environment on a floppy that I could stick in anyone's machine and make it usable.
* We had a source license for Mince, orphaned by Mark of the Unicorn, a tiny emacs-clone that ran on CP/M, MS-DOS, and Unix. We had enhanced it significantly.
Hmmz, I was hoping my post was without any judgement about what is 'better' and more '133t' coding. Sorry you think otherwise :(
Some people like their code to run on OSes for grownups.
"Single instance only" applied to all code - applications, libraries and OS. We often used to have 16 users on an 11/70 with 1MW of memory (ie 2MB) - all running the same program, so only one copy was resident. (or one of us was running the C or Fortran compilers :-)
isn't that how the BSDs do it today?
In RSX/11, programs could be "installed" so that they made their location on disk known to the OS, so when you ran a program, it was not necessary to search the file system for it. The location on disk, and offset to the entry point, was already known. A program could have multiple entry points (like grep, egrep etc), and libraries just used this mechanism. The dynamic linker stored the program (library) name and index into a table of entry points. I think early implementations statically linked the code to hack this stuff, before it became part of the OS.
If the search of the program you asked for found nothing, then the directories were searched. It was laziness of the users that meant the default strategy was used for most applications. I think VMS continued to support the install option, but I cant remember. I don't think Un*x ever did.
Programs only loaded the pages that were in use, and pages not in use were eventually swapped out. So huge programs did not take for ever to load - you loaded the first page, and jumped to it - then loaded which ever pages execution went to - so you did not need to spend years designing overlay strategies! This was possible because pages could load anywhere - the PDP11 supported "position independent code" (All modern 16 and 32 bit processors could still do this).
Don't you young people know anything? I know this, and I didn't even do computer science in college!
Get off my lawn.
Sent from my ASR33 using ASCII
I think VMS continued to support the install option, but I cant remember. I don't think Un*x ever did.
IIRC install in VMS was to register a privileged library with the OS. A library like that could do stuff the calling process couldn't do. Most likely it was install image.obj/priv=sysprv,setprv and so on.
My experience with RSX was with a traffic signal application called SCATS. I once interviewed for a job in a hospital where they supported ~60 users on a single machine, probably an 11/84.
Our SCATS systems had up to 16 DZ11 MUX cards for 128 serial lines. I have never seen a system which could handle that many interrupts and run so cool in the sense that it was always responsive regardless of load and it would chug away for years without showing any signs of stress.
BSD is as close as you would get to that with modern systems. Maybe QNX though I haven't worked with that OS.
http://michaelsmith.id.au
After reading the linked article, I thought underwhelmed. Then I read the second article referenced in the summary:
http://www.muppetlabs.com/~breadbox/software/tiny/teensy.html
Now, that was interesting!
The strange thing is that the summary seems to imply that both articles are related, which they are most definitely not. The first one seems to be written by a naive noob, who just discovered a nifty trick in gcc. The second one is written by a real Wizard, who shows you how to conjure up some arcane magic to make ELF your bitch.
-dZ.
Carol vs. Ghost
...besides, high-level programmers often underestimate just how big a sector embedded programming is. The $IDIOTS_PET_LANGUAGE is for a PC. Now get me more RAM and better CPU for all the devices running embedded software, that are in my sight range as I look around:
- my cell phone.
- 6 different monitors (OSD doesn't happen magically. Something remembers the settings...)
- a videoserver
- 2 cheap switches
- a regulated power supply
- a heat-controlled soldering iron
- a regular phone
- 3 PC keyboards (hey, neither PS2 nor USB protocols happen by themselves)
- 3 computer mice (optical, meaning pretty advanced image analysis)
- my hand watch
- a battery charger
- a USB hub
- a security motion sensor
- an MP3 player
- a webcam
- a multimeter
- a car alarm remote
- a pendrive.
These all were programmed either in VHDL, Asembler, or C. The phone has some J2ME code too. Think of upgrading each of these devices so much that its firmware could be rewritten in, say, Perl. Or C#.
Also, think about how much embedded programming is in every PC. Each device controller has its own firmware... my bet is any average house contains more embedded programs (in embedded devices) than PC applications on the "family PC" and stored on media.
High-level programming languages are nice and have their place, but considering embedded "a niche not worthy of attention" is a bad mistake. The proportions between amounts of server:desktop:embedded software are much closer to 1:1:1 than most "high-level" programmers are willing to admit.
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
Was that in RSX11-M?
Version 6 UNIX. I didn't abuse a.out as badly as this example abuses elf, though.
Really, with a.out, it wasn't abuse. That format LIKED these kinds of games. When I was hacking in Forth I wrote a "snapshot" word that did something like
Where patch-to-executable took advantage of the fact that an a.out was basically a core dump with some extra segments... and you could leave those segments off if you needed to. :)
I did some nasty stuff on RSX-11, though. Portable file and terminal I/O was a pain in the butt, because text files were variant record files with each line having a count and a length and a record/line type field and IIRC occasional block alignment issues, so to read and write text files in Forth I had a FORTRAN main that called Forth through an assembly glue routine, then called back to FORTRAN for textfile I/O. Also got tired of FORTRAN formatted I/O so I wrote a version of sprintf for my RATFOR code that used assembly glue to implement varargs in FORTRAN. Ah, the good old days...