En que escribir un manual de programacion

Si la intención es hacer un manual para ti mismo, entonces supongo que la estética tiene prioridad, y en ese caso podrías utilizar directamente Html u otro lenguaje de markups como por ejemplo MarkDown, con cualquier editor de MarkDown como por ejemplo MarkDownPad: http://markdownpad.com/ aunque en mi opinión personal sería más recomendable utilizar cualquier editor de CHM profesional (los hay que se parecen a Microsoft Word, donde puedes arrastrar imágenes y videos, crear listas, tablas, y hacer de todo un poco) para generar un archivo de ayuda compilada en Html, sería estéticamente mucho más bonito y profesional que esto, pero bueno, ya que buscas sencillez te propongo la opción estética que a mi me parece más sencilla: MarkDown.

Código markdown:

Código

## Welcome to MarkdownPad 2 ##
 
**MarkdownPad** is a full-featured Markdown editor for Windows.
 
----------
 
## How to ping a IP in C# ##
 
**Import namespaces:**
 
    using System.Net.NetworkInformation;
 
**Code:**
 
    Ping ping = new Ping();
    PingReply pingReply = ping.Send("81.2.199.57");
 
    Console.WriteLine("Address: {0}", pingReply.Address);
    Console.WriteLine("Time in miliseconds: {0}", pingReply.RoundtripTime);
    Console.WriteLine("Status: {0}", pingReply.Status);
 
**Console Output:**
 
    Address: 81.2.199.57
    Time in miliseconds: 6
    Status: Success

Código Html generado:

Código:

<!DOCTYPE html>
<html>
<head>
<title>MarkdownPad Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
/* GitHub stylesheet for MarkdownPad (http://markdownpad.com) */
/* Author: Nicolas Hery - http://nicolashery.com */
/* Version: b13fe65ca28d2e568c6ed5d7f06581183df8f2ff */
/* Source: https://github.com/nicolahery/markdownpad-github */

/* RESET
=============================================================================*/

html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
  margin: 0;
  padding: 0;
  border: 0;
}

/* BODY
=============================================================================*/

body {
  font-family: Helvetica, arial, freesans, clean, sans-serif;
  font-size: 14px;
  line-height: 1.6;
  color: #333;
  background-color: #fff;
  padding: 20px;
  max-width: 960px;
  margin: 0 auto;
}

body>*:first-child {
  margin-top: 0 !important;
}

body>*:last-child {
  margin-bottom: 0 !important;
}

/* BLOCKS
=============================================================================*/

p, blockquote, ul, ol, dl, table, pre {
  margin: 15px 0;
}

/* HEADERS
=============================================================================*/

h1, h2, h3, h4, h5, h6 {
  margin: 20px 0 10px;
  padding: 0;
  font-weight: bold;
  -webkit-font-smoothing: antialiased;
}

h1 tt, h1 code, h2 tt, h2 code, h3 tt, h3 code, h4 tt, h4 code, h5 tt, h5 code, h6 tt, h6 code {
  font-size: inherit;
}

h1 {
  font-size: 28px;
  color: #000;
}

h2 {
  font-size: 24px;
  border-bottom: 1px solid #ccc;
  color: #000;
}

h3 {
  font-size: 18px;
}

h4 {
  font-size: 16px;
}

h5 {
  font-size: 14px;
}

h6 {
  color: #777;
  font-size: 14px;
}

body>h2:first-child, body>h1:first-child, body>h1:first-child+h2, body>h3:first-child, body>h4:first-child, body>h5:first-child, body>h6:first-child {
  margin-top: 0;
  padding-top: 0;
}

a:first-child h1, a:first-child h2, a:first-child h3, a:first-child h4, a:first-child h5, a:first-child h6 {
  margin-top: 0;
  padding-top: 0;
}

h1+p, h2+p, h3+p, h4+p, h5+p, h6+p {
  margin-top: 10px;
}

/* LINKS
=============================================================================*/

a {
  color: #4183C4;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* LISTS
=============================================================================*/

ul, ol {
  padding-left: 30px;
}

ul li > :first-child,
ol li > :first-child,
ul li ul:first-of-type,
ol li ol:first-of-type,
ul li ol:first-of-type,
ol li ul:first-of-type {
  margin-top: 0px;
}

ul ul, ul ol, ol ol, ol ul {
  margin-bottom: 0;
}

dl {
  padding: 0;
}

dl dt {
  font-size: 14px;
  font-weight: bold;
  font-style: italic;
  padding: 0;
  margin: 15px 0 5px;
}

dl dt:first-child {
  padding: 0;
}

dl dt>:first-child {
  margin-top: 0px;
}

dl dt>:last-child {
  margin-bottom: 0px;
}

dl dd {
  margin: 0 0 15px;
  padding: 0 15px;
}

dl dd>:first-child {
  margin-top: 0px;
}

dl dd>:last-child {
  margin-bottom: 0px;
}

/* CODE
=============================================================================*/

pre, code, tt {
  font-size: 12px;
  font-family: Consolas, "Liberation Mono", Courier, monospace;
}

code, tt {
  margin: 0 0px;
  padding: 0px 0px;
  white-space: nowrap;
  border: 1px solid #eaeaea;
  background-color: #f8f8f8;
  border-radius: 3px;
}

pre>code {
  margin: 0;
  padding: 0;
  white-space: pre;
  border: none;
  background: transparent;
}

pre {
  background-color: #f8f8f8;
  border: 1px solid #ccc;
  font-size: 13px;
  line-height: 19px;
  overflow: auto;
  padding: 6px 10px;
  border-radius: 3px;
}

pre code, pre tt {
  background-color: transparent;
  border: none;
}

kbd {
   -moz-border-bottom-colors: none;
   -moz-border-left-colors: none;
   -moz-border-right-colors: none;
   -moz-border-top-colors: none;
   background-color: #DDDDDD;
   background-image: linear-gradient(#F1F1F1, #DDDDDD);
   background-repeat: repeat-x;
   border-color: #DDDDDD #CCCCCC #CCCCCC #DDDDDD;
   border-image: none;
   border-radius: 2px 2px 2px 2px;
   border-style: solid;
   border-width: 1px;
   font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
   line-height: 10px;
   padding: 1px 4px;
}

/* QUOTES
=============================================================================*/

blockquote {
  border-left: 4px solid #DDD;
  padding: 0 15px;
  color: #777;
}

blockquote>:first-child {
  margin-top: 0px;
}

blockquote>:last-child {
  margin-bottom: 0px;
}

/* HORIZONTAL RULES
=============================================================================*/

hr {
  clear: both;
  margin: 15px 0;
  height: 0px;
  overflow: hidden;
  border: none;
  background: transparent;
  border-bottom: 4px solid #ddd;
  padding: 0;
}

/* TABLES
=============================================================================*/

table th {
  font-weight: bold;
}

table th, table td {
  border: 1px solid #ccc;
  padding: 6px 13px;
}

table tr {
  border-top: 1px solid #ccc;
  background-color: #fff;
}

table tr:nth-child(2n) {
  background-color: #f8f8f8;
}

/* IMAGES
=============================================================================*/

img {
  max-width: 100%
}
</style>
</head>
<body>
<h2>Welcome to MarkdownPad 2</h2>
<p><strong>MarkdownPad</strong> is a full-featured Markdown editor for Windows.</p>
<hr />
<h2>How to ping a IP in C#</h2>
<p><strong>Import namespaces:</strong></p>
<pre><code>using System.Net.NetworkInformation;
</code></pre>

<p><strong>Code:</strong></p>
<pre><code>Ping ping = new Ping();
PingReply pingReply = ping.Send("81.2.199.57");

Console.WriteLine("Address: {0}", pingReply.Address);
Console.WriteLine("Time in miliseconds: {0}", pingReply.RoundtripTime);
Console.WriteLine("Status: {0}", pingReply.Status);
</code></pre>

<p><strong>Console Output:</strong></p>
<pre><code>Address: 81.2.199.57
Time in miliseconds: 6
Status: Success
</code></pre>

</body>
</html>

Renderización del navegador:

Si por lo contrario la estética te importa 3 pitos y lo que quieres es un editor de código donde poder escribir/desarrollar tus códigos de forma sencilla y eficiente, entonces el editor Visual Studio Code sería una opción inteligente y sofisticada gracias al motor IntelliSense de Microsoft, el cual te permitirá autocompletar la sintaxis de casi cualquier lenguaje de programación, eso por no mencionar el resto de funcionalidades únicas que tiene, las cuales aumentarán tu rendimiento como programador en comparación con otros editores y/o IDEs.

A menos que especifiques el lenguaje que estás usando, no te puedo dar una opción menos "global" que VS Code. Sublime Text también está muy bien, pero carece de funcionalidades en comparación y su autocompletado deja bastante que desear.

¡Saludos!