1.1.8. Learning to learn

There are a few concepts to point out about learning programming.

When learning a programming language, there are a few different areas that need to be learned. One is the syntax. For example, the syntax for branches in Python looks like this:

if a > 5:
    print 'a is greater than 5'

While for example in C it would look like this:

if(a > 5) {
    printf("a is greater than 5\n");
}

Another is the standard library, i.e. the library included as part of the language implementation. For example, as part of its standard library, Python has a module for math functions, called “math”:

import math

print math.sqrt(5)
print math.pi

The “math” module has lots of functions, and the reference for them can be accessed in the Python interpreter e.g. by running the following commands:

$ python2
Python 2.7.13 (default, Dec 21 2016, 07:16:46)
[GCC 6.2.1 20160830] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> help(math)

That is, on line 1 we run “python2” in shell to start the Python interactive interpreter. On line 5 we import the math module, and on line 6 we ask for the help for that module.

Exercise: Check out the help for the math module in Python. You can exit the help screen by pressing “q”. You can exit the Python interpreter by pressing ctrl+d.

The concept of reference is important: it’s a factual listing of a library or a programming language. It typically doesn’t include examples or tutorials but is useful for getting a deeper understanding of a subject.

As another example, we will introduce the Unix command “ls”, a tool for listing files. In order to gain initial understanding of this tool, this book will give a couple of examples:

$ ls
genindex.html  index.html  objects.inv                regex.html   searchindex.js  _static
_images        js.html     python_generate_file.html  search.html  _sources        unix.html
$ ls -l
total 108
drwxr-xr-x 2 antti users  4096 Feb  5 23:51 _images
drwxr-xr-x 2 antti users  4096 Feb  7 00:48 _sources
drwxr-xr-x 2 antti users  4096 Feb  5 23:51 _static
-rw-r--r-- 1 antti users  2603 Feb  7 23:33 genindex.html
[...]

This example shows that merely running “ls” will list the files, while adding the switch “-l” will give more information, such as the last modify time of the files. However, “ls” has a lot more possible switches which are not all covered in this book, although they will become useful and will to some extent be necessary to use, learn and understand as a software engineer. Hence it’ll be important to refer to the reference of the command to get an overview. This can typically be done either by passing the switch “–help” to the relevant command, or reading the manual for the command (by running “man”, e.g. “man ls”). For example:

$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
[...]

If you run “man ls” you’ll open the manual page which you can exit by pressing “q”.

Exercise: Open the manual page for ls.

The same principle applies not only to Unix commands, but also to programming languages as well as standard and non-standard libraries. For example, for most programming languages there is either a language specification or reference material available which should be consulted whenever questions arise about a specific behaviour in a programming language. Similarly, libraries typically come with references. The standard library for C is included in the Unix man pages, such that for example running “man scanf” will present a detailed documentation of the scanf() function family. For other libraries, the website of the library or other similar material should be consulted. Many libraries also install their own man pages as part of the library installation.

Terminology wise, this book will use the terms “API” and “library” interchangeably. The acronym “API” stands for “Application Programming Interface” and generally means the interface, i.e. the available functions, variables and other constructs, that a library provides to make use of the library. For example, if one were to use the libcurl library, a library for downloading files via URLs, one would want to find the reference of the library on the web page of the software.

Exercise: Look up the man page for printf().

Exercise: Find the reference of the libcurl library online. See if you can find both the entry point to the reference as well as the reference of a specific libcurl function, for example curl_easy_init().