Sharp EL-9300 Graphics Calculator, 296 bytes

This was my secondary school graphing calculator, getting on for 20 years ago! I remember writing a mandelbrot generator for it way back then. And sure enough, its still sitting there in the NV memory:

ClrG
DispG
Range -2.35,2.35,.5,-1.55,1.55,0.5
y=-1.55
Label ly
x=-2.35
Label lx
n=1
zx=0
zy=0
Label ln
tzx=zx²-zy²+x
zy=(2*zx*zy)+y
zx=tzx
If zx²+zy²>4Goto esc
n=n+1
If n<20Goto ln
Label esc
If fpart (n/2)=0Goto npl
Plot x,y
Label npl
x=x+.05
If x<=2.35Goto lx
y=y+.05
If y<=1.55Goto ly
Wait

It took about 90 minutes to render.

This is totally ungolfed. I'm sure I could save a bit of space, but I just wanted to share this historical curiosity!

I love that the only control statements available are gotos.

Here's a photo. I don't have any other means to get the graphical output out:

LaTeX, 673 bytes

\countdef\!1\!129\documentclass{article}\usepackage[margin=0pt,papersize=\!bp]{geometry}\usepackage{xcolor,pgf}\topskip0pt\offinterlineskip\def~{99}\let\rangeHsb~\countdef\c2\countdef\d3\countdef\e4\begin{document}\let\a\advance\let\p\pgfmathsetmacro\makeatletter\def\x#1#2#3{#10
\@whilenum#1<#2\do{#3\a#11}}\d0\x\c{\numexpr~+1}{\expandafter\edef\csname\the\c\endcsname{\hbox{\noexpand\color[Hsb]{\the\d,1,1}\/}}\a\d23
\ifnum\d>~\a\d-~\fi}\def\/{\rule{1bp}{1bp}}\x\c\!{\hbox{\x\d\!{\p\k{4*\d/(\!-1)-2}\p\K{2-4*\c/(\!-1)}\def\z{0}\def\Z{0}\x\e~{\p\:{\z*\z-\Z*\Z+\k}\p\Z{2*\z*\Z+\K}\let\z\:\p\:{\z*\z+\Z*\Z}\ifdim\:pt>4pt\csname\the\e\endcsname\e~\fi}\ifnum\e=~\/\fi}}}\stop

(129 × 129)

The PDF image consists of colored square units with size 1bp × 1bp.

Ungolfed

% count register \size contains the width and height of the square
\countdef\size=1
\size=31
\documentclass{article}
\usepackage[margin=0pt,papersize=\size bp]{geometry}
\usepackage{xcolor,pgf}
\topskip0pt
\offinterlineskip
\def\iterations{99}
\let\rangeHsb\iterations
\countdef\c2
\countdef\d3
\countdef\e4
\begin{document}
\let\p\pgfmathsetmacro
\makeatletter
% \Loop: for (#1 = 0; #1 < #2; #1++) {#3}
\def\Loop#1#2#3{%
  #1=0
  \@whilenum#1<#2\do{#3\advance#11}%
}
\d0%
\Loop\c{\numexpr\iterations+1\relax}{%
  \expandafter\edef\csname\the\c\endcsname{%
    \hbox{\noexpand\color[Hsb]{\the\d,1,1}\noexpand\pixel}%
  }%
  \advance\d23 \ifnum\d>\iterations\advance\d-\iterations\fi
}
\def\pixel{\rule{1bp}{1bp}}
% \c: row
% \d: column
% \e: iteration
\Loop\c\size{%
  \typeout{c: \the\c}%
  \hbox{%
    \Loop\d\size{%
      \pgfmathsetmacro\k@re{4*\d/(\size-1)-2}%
      \pgfmathsetmacro\K@im{2-4*\c/(\size-1)}%
      \def\z@re{0}%
      \def\Z@im{0}%
      \Loop\e\iterations{%
         % calculate z(n+1) = z^2(n) + k
         \pgfmathsetmacro\temp{\z@re*\z@re-\Z@im*\Z@im+\k@re}%
         \pgfmathsetmacro\Z@im{2*\z@re*\Z@im+\K@im}%
         \let\z@re\temp
         % calculate abs(z)^2
         \pgfmathsetmacro\temp{\z@re*\z@re+\Z@im*\Z@im}%
         \ifdim\temp pt>4pt\csname\the\e\endcsname\e\iterations\fi
      }%   
      \ifnum\e=\iterations\pixel\fi
    }%
  }%
}
\stop

I came across this the other day. I don't take credit for it, but damn, is it awesome:

Python:

_                                      =   (
                                        255,
                                      lambda
                               V       ,B,c
                             :c   and Y(V*V+B,B,  c
                               -1)if(abs(V)<6)else
               (              2+c-4*abs(V)**-0.4)/i
                 )  ;v,      x=1500,1000;C=range(v*x
                  );import  struct;P=struct.pack;M,\
            j  ='<QIIHHHH',open('M.bmp','wb').write
for X in j('BM'+P(M,v*x*3+26,26,12,v,x,1,24))or C:
            i  ,Y=_;j(P('BBB',*(lambda T:(T*80+T**9
                  *i-950*T  **99,T*70-880*T**18+701*
                 T  **9     ,T*i**(1-T**45*2)))(sum(
               [              Y(0,(A%3/3.+X%v+(X/v+
                               A/3/3.-x/2)/1j)*2.5
                             /x   -2.7,i)**2 for  \
                               A       in C
                                      [:9]])
                                        /9)
                                       )   )

http://preshing.com/20110926/high-resolution-mandelbrot-in-obfuscated-python/

Java - 505...383 370

Just a standard calculation, with golfitude added.

Golfed:

public class M{public static void main(String[]v){int n=640,t,s,i=n*n;final BufferedImage z=new BufferedImage(n,n,1);Frame f=new Frame(){public void paint(Graphics g){g.drawImage(z,0,28,null);}};for(f.setSize(n,668);--i>0;z.setRGB(i/n,i%n,s*820)){float c=4f/n,a=c*i/n-2,b=i%n*c-2,r=a,e=b,p;for(s=t=99;t-->0&&r*r+e*e<4;s=t,p=r*r-e*e+a,e=r*e*2+b,r=p);}f.setVisible(1>0);}}

With line breaks:

public class M{
    public static void main(String[]v){
        int n=640,t,s,i=n*n;
        final BufferedImage z=new BufferedImage(n,n,1);
        Frame f=new Frame(){
            public void paint(Graphics g){
                g.drawImage(z,0,28,null);
            }
        };      
        for(f.setSize(n,668);--i>0;z.setRGB(i/n,i%n,s*820)){
            float c=4f/n,a=c*i/n-2,b=i%n*c-2,r=a,e=b,p;
            for(s=t=99;t-->0&&r*r+e*e<4;s=t,p=r*r-e*e+a,e=r*e*2+b,r=p);
        }
        f.setVisible(1>0);
    }
}

x86 DOS Assembly - 208 177

The full binary, in HEX, is:

9BDBE3BE0010B81300CD106800A007BF87F9FDBAC7008BCAE81A008AC3AA4979F7B9C70083EF784A79EE33C0CD16B80300CD10CD208BC12D640089441CDF441CDF06AB01DEF9D95C088BC22D640089441CDF441CDF06AB01DEF9D95C0CD9EED914D95404D95410D95C14B301D904D84C04DE0EAD01D8440CD95404D94410D86414D84408D914D80CD95C10D84C04D95414D84410DF06AF01DED99BDFE09B9E7209FEC380FBC872C432DBC3320002000400

The sample image is:

The full source in readable ASM is fairly long. I have put it up at: Full Source

This is designed for compiling with TASM, runs in MCGA, and waits for a keypress before ending the program. The colors are just the default MCGA palette.

EDIT: Optimized it, now it draws backwards (same image though), and saved 31 bytes!

Mathematica 214 191 215

Back to Black

My earlier submission did not meet the requirement to leave the inside all black (or white). This does.

m=Compile[{{c,_Complex}},Length[FixedPointList[#^2+c&,0,99,SameTest→(Abs@#>=2&)]]];
ArrayPlot[Table[m[a+I b],{b,-2,2,.01},{a,-2,2,.01}],DataRange→{{-2,2},{-2,2}},
ColorRules→{100→Black},ColorFunction→(Hue[Log[34,#]]&)]

Javascript (ECMAScript 6) - 315 Characters

document.body.appendChild(e=document.createElement("canvas"));v=e.getContext("2d");i=v.createImageData(e.width=e.height=n=600,n);j=0;k=i.data;f=r=>k[j++]=(n-c)*r%256;for(y=n;y--;)for(x=0;x++<n;){c=s=a=b=0;while(c++<n&&a*a+b*b<5){t=a*a-b*b;b=2*a*b+y*4/n-2;a=t+x*4/n-2}f(87);f(0);f(0);k[j++]=255}v.putImageData(i,0,0)

JSFIDDLE - Requires Firefox (as the only browser to have, so far, implemented ECMAScript 6 arrow functions)

• Change n to vary the image size (and number of iterations).
• Change the values passed in the f(87);f(0);f(0); calls (near the end) to change the RGB colour values. (f(8);f(8);f(8); is greyscale.)

With f(8);f(23);f(87);:

R, 199 211 characters

Old solution at 199 characters:

r=seq(-2,2,l=500);c=t(sapply(r,function(x)x+1i*r));d=z=array(0,dim(c));a=1:25e4;for(i in 1:99){z[a]=c[a]+z[a]^2;s=abs(z[a])<=2;d[a[!s]]=i;a=a[s]};image(d,b=0:99,c=c(1,sample(rainbow(98))),ax=F,asp=1)

With indentation:

r=seq(-2,2,l=500)
c=t(sapply(r,function(x)x+1i*r)) #Produces the initial imaginary number matrix
d=z=array(0,dim(c)) #empty matrices of same size as c 
a=1:25e4            #(z will store the magnitude, d the number of iterations before it reaches 2)
for(i in 1:99){     #99 iterations
    z[a]=c[a]+z[a]^2
    s=abs(z[a])<=2
    d[a[!s]]=i
    a=a[s]
    }
image(d,b=0:99,c=c(1,sample(rainbow(98))),ax=F,asp=1) #Colors are randomly ordered (except for value 0)

Edit: Solution at 211 characters that colors the inside of the set and the outside of the first layer differently:

r=seq(-2,2,l=500);c=t(sapply(r,function(x)x+1i*r));d=z=array(0,dim(c));a=1:25e4;for(i in 1:99){z[a]=c[a]+z[a]^2;s=abs(z[a])<=2;d[a[!s]]=i;a=a[s]};d[a[s]]=-1;image(d,b=-1:99,c=c(1:0,sample(rainbow(98))),ax=F,asp=1)

With indentation:

r=seq(-2,2,l=500)
c=t(sapply(r,function(x)x+1i*r))
d=z=array(0,dim(c))
a=1:25e4
for(i in 1:99){
    z[a]=c[a]+z[a]^2
    s=abs(z[a])<=2
    d[a[!s]]=i
    a=a[s]
    }
d[a[s]]=-1 #Gives the inside of the set the value -1 to differenciate it from value 0.
image(d,b=-1:99,c=c(1,sample(rainbow(99))),ax=F,asp=1)

Python w/ PIL - 166 bytes

import Image
d=600;i=Image.new('RGB',(d,d))
for x in range(d*d):
 z=o=x/9e4-2-x%d/150.j-2j;c=99
 while(abs(z)<2)*c:z=z*z+o;c-=1
 i.putpixel((x/d,x%d),5**8*c)
i.show()

Output (will open in the default *.bmp viewer):

Java - Processing (271 bytes)

void setup(){int h=100,e=5*h,i;float d,v,w,a,b,c;size(e,e);colorMode(HSB,h);loadPixels();d=4./e;v=2;for(int x=1;x<=e;x++){v-=d;w=2;for(int y=0;y<e;){w-=d;a=b=c=0;i=-1;while(a*a+b*b<4&&++i<h){c=a*a-b*b+v;b=2*a*b+w;a=c;}pixels[e*++y-x]=color(i*9%h,h,h-i);}}updatePixels();}

Expanded:

void setup(){
  int h=100, e=5*h, i; //init of size "e", max hue "h", iterator "i"
  float d,v,w,a,b,c; //init of stepwidth "d", y-coord "v", x-coord "w", Re(z) "a", Im(z) "b", temp_a "c"
  size(e,e);
  colorMode(HSB,h);
  loadPixels();
  d = 4./e;
  v = 2;
  for(int x = 1; x <= e; x++){
    v -= d;
    w = 2;
    for(int y = 0; y < e;){
      w -= d;
      a = b = c = 0;
      i = -1;
      while(a*a + b*b < 4 && ++i < h){
        c = a*a - b*b + v;
        b = 2*a*b + w;
        a = c;
      }
      pixels[e * ++y - x] = color(i*9 % h, h, h-i);
    }
  }
  updatePixels();
}

JavaScript + HTML5 (356B)

(Note: lines ending with '//' are added here for some readability)

Performant version (375B):

<body onload='var
w,h=w=C.width=C.height=500,X=C.getContext("2d"),I=X.createImageData(w,h),D=I.data, //
y=0,f=255,T=setInterval(function(x,i,j,k,l,c,o){for(x=0;x<w;){                     //
for(i=x*4/w-2,j=y*4/h-2,k=l=0,c=f;--c&&k*k+l*l<4;)t=k*k-l*l+i,l=2*k*l+j,k=t
D[o=(y*w+x++)*4]=(c*=0xc0ffeeee)&f
D[++o]=c>>8&f
D[++o]=c>>16&f
D[++o]=f}X.putImageData(I,0,0)
++y-h||clearInterval(T)},0)'><canvas id=C>

Slow version (356B): remove the 'var' and parameters in the inner function so that the global scope is used.

Try it out: http://jsfiddle.net/neuroburn/Bc8Rh/

C + Allegro - 248 bytes

#include<allegro.h>
x=-1,y,K=400;float a,h,c,d,k;main(i){set_gfx_mode('SAFE',K,K,allegro_init(),0);while(x++<K)
for(y=0;y<K;y++){for(a=h=i=0;a*a+h*h<4&&++i<256;k=a,a=a*a-h*h+x*0.01-2,h=2*k*h+y*0.01-2);
putpixel(screen,x,y,i);}while(1);}END_OF_MAIN()

Output:

Octave (212 143 bytes)

[x,y]=meshgrid(-2:.01:2);z=c=x+i*y;m=0*e(401);for n=0:99;m+=abs(z)<2;z=z.^2+c;end;imagesc(m);colormap([hsv(128)(1+mod(0:79:7900,128),:);0,0,0])

With whitespace:

[x,y] = meshgrid(-2:.01:2);
z = c = x + i*y;
m = 0*e(401);
for n=0:99
    m += abs(z)<2;
    z = z.^2 + c;
end
imagesc(m)
colormap([hsv(128)(1+mod(0:79:7900,128),:);
          0,0,0])

Output:

This would likely work on Matlab too. (Last time I used Matlab, it did not support +=, so fixing that might add one byte. But that was a long time ago.)

My first answer (212 bytes):

[x,y]=meshgrid(-2:.01:2);z=c=x+i*y;m=0*e(401);for n=0:99;m+=abs(z)<2;z=z.^2+c;endfor;t=[0*e(1,7);2.^[6:-1:0]];[s{1:7}]=ndgrid(num2cell(t,1){:});t=1+sum(cat(8,s{:}),8);imagesc(m);colormap([hsv(128)(t(:),:);0,0,0])

BBC Basic (228 bytes)

What about languages that nobody ever heard of in code golf? Most likely could be optimized, but I'm not quite where - improvements possible. Based of http://rosettacode.org/wiki/Mandelbrot_set#BBC_BASIC, but I tried to code golf it as much as possible.

VDU23,22,300;300;8,8,8,8
ORIGIN0,300
GCOL1
FORX=0TO600STEP2
i=X/200-2
FORY=0TO300STEP2
j=Y/200
x=0
y=0
FORI=1TO128
IFx*x+y*y>4EXIT FOR
t=i+x*x-y*y
y=j+2*x*y
x=t
NEXT
COLOUR1,I*8,I*4,0
PLOTX,Y:PLOTX,-Y
NEXT
NEXT

The > symbol on image is prompt, and it's automatically generated after running the program.

Python with Pylab+Numpy 151 Bytes

I couldn't bear to see a non-DQ'ed Python entry, but I think I really outdid myself on this one, and I made it down to 153 characters!

import numpy as n
from pylab import*
i=99
x,y=n.mgrid[-2:2:999j,-2:2:999j]
c=r=x*1j+y
x-=x
while i:x[(abs(r)>2)&(x==0)]=i;r=r*r+c;i-=1
show(imshow(x))

Also, notably, the second to last line raises 4 distinct runtime warnings, a new personal record!

GLSL - 225 bytes:

void main(){vec2 c=gl_FragCoord.xy/iResolution.y*4.-2.,z=c,v;for(int i=0;i<99;i++){z=vec2(z.x*z.x-z.y*z.y,2.*z.x*z.y)+c;if(length(z)>2.&&v.y<1.)v=vec2(float(i)/99.,1.);}gl_FragColor=(v.y<1.)?vec4(v,v):texture2D(iChannel0,v);}

See it in ShaderToy

This requires a suitable palette texture be loaded as iChannel0. (The colouring here is from the "random pixel" texture on ShaderToy).

Perl + GD, 264

$I=new GD::Image $s=499,$s;Z(0,0,0);Z(map rand 256,1..3)for
0..99;for$x(0..$s){for$y(0..$s){for($H=$K=$c=$t=0;$c++<99&&$H*$H+$K*$K<4;){sub
Z{$I->colorAllocate(@_)}($H,$K)=($H*$H-$K*$K+4*$x/$s-2,2*$H*$K+4*$y/$s-2)}use
GD;$I->setPixel($x,$y,$c<99&&$c)}}print $I->png

Golfed from this code

gnuplot 116 (111 without newlines)

Obligatory gnuplot entry. It's been done countless times but this one is from scratch (not that it's difficult). I like how gnuplot golfs its commands intrinsically :)

f(z,w,n)=abs(z)>2||!n?n:f(z*z+w,w,n-1)
se vi map
se si sq
se isos 256
sp [-2:2] [-2:2] f(0,x*{1,0}+y*{0,1},99) w pm

ungolfed:

f(z,w,n)=abs(z)>2||n==0?n:f(z*z+w,w,n-1)
set view map
set size square
set isosamples 256
splot [-2:2] [-2:2] f(0,x*{1,0}+y*{0,1},99) with pm3d

However, I'm DEEPLY disappointed at the entry of complex numbers. x*{1,0}+y*{0,1} must be the saddest existing way of constructing a complex number.

Oops, the image:

Set isosamples higher for better resolution. We could also say unset tics and unset colorbox for a pure image, but I think this version qualifies just fine.

J, 72

load'viewmat'
(0,?$~99 3)viewmat+/2<|(j./~i:2j479)(+*:) ::(3:)"0^:(i.99)0