update README
diff --git a/README.md b/README.md
index 2c22dc4..4031d5d 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,20 @@
+# About
-# Installation
+ASN.1 to C compiler takes the ASN.1 module files (example) and generates
+the C++ compatible C source code. That code can be used to serialize
+the native C structures into compact and unambiguous BER/XER/PER-based
+data files, and deserialize the files back.
+
+Various ASN.1 based formats are widely used in the industry,
+such as to encode the X.509 certificates employed in the HTTPS handshake,
+to exchange control data between mobile phones and cellular networks,
+to car-to-car communication in intelligent transportation networks.
+
+The ASN.1 standard is large and complex and no open source compiler supports
+it in its entirety. The asn1c is arguably the most evolved open source
+ASN.1 compiler.
+
+# Build and Install
If you haven't installed the asn1c yet, read the [INSTALL](INSTALL) file for a
short installation guide.
@@ -8,11 +23,7 @@
For the list of asn1c command line options, see `asn1c -h` or `man asn1c`.
-The comprehensive documentation on this compiler is in [asn1c-usage.pdf](doc/asn1c-usage.pdf).
-
-If you are building the compiler from the sources, the PDFs reside
-in the ./doc directory. Normally the file is installed together with the
-README.md file you're reading right now.
+The comprehensive documentation on this compiler is in [doc/asn1c-usage.pdf](doc/asn1c-usage.pdf).
Please also read the [FAQ](FAQ) file.
@@ -21,31 +32,33 @@
# Quick start
-(also check out [asn1c-quick.pdf](doc/asn1c-quick.pdf))
+(also check out [doc/asn1c-quick.pdf](doc/asn1c-quick.pdf))
-After building [and installing] the compiler (see INSTALL), you may use
+After installing the compiler (see [INSTALL](INSTALL)), you may use
the asn1c command to compile the ASN.1 specification:
asn1c <module.asn1> # Compile module
If several specifications contain interdependencies, all of them must be
-specified:
+specified at the same time:
asn1c <module1.asn1> <module2.asn1> ... # Compile interdependent modules
-If you are building the asn1c from the sources, the ./examples directory
-contains several ASN.1 modules and a script to extract the ASN.1 modules
-from RFC documents. Refer to the README file in that directory.
+The asn1c source tarball contains the [examples/](examples/) directory
+with several ASN.1 modules and a [script](examples/crfc2asn1.pl)
+to extract the ASN.1 modules from RFC documents.
+Refer to the [examples/README](examples/README) file in that directory.
+
To compile the X.509 PKI module:
./asn1c/asn1c -P ./examples/rfc3280-*.asn1 # Compile-n-print
-In this example, -P option is used to instruct the compiler to print the
-compiled text on the standard output instead of creating multiple .c
-and .h files for every ASN.1 type found inside the specified ASN.1 modules.
-This is useful for debugging and test automation.
+In this example, the **-P** option is to print the compiled text on the
+standard output. The default behavior is that asn1c compiler creates
+multiple .c and .h files for every ASN.1 type found inside the specified
+ASN.1 modules.
-The compiler -E and -EF options are used for testing the parser and
+The compiler's *-E* and *-EF* options are used for testing the parser and
the semantic fixer, respectively. These options will instruct the compiler
to dump out the parsed (and fixed) ASN.1 specification as it was
"understood" by the compiler. It might be useful for checking
@@ -59,12 +72,12 @@
The asn1c compiler works by processing the ASN.1 module specifications
in several stages:
-1. In the first stage, the ASN.1 file is parsed.
+1. During the first stage, the ASN.1 file is parsed.
(Parsing produces an ASN.1 syntax tree for the subsequent levels)
-2. In the second stage, the syntax tree is "fixed".
+2. During the second stage, the syntax tree is "fixed".
(Fixing is a process of checking the tree for semantic errors,
accompanied by the tree transformation into the canonical form)
-3. In the third stage, the syntax tree is compiled into the target language.
+3. During the third stage, the syntax tree is compiled into the target language.
There are several command-line options reserved for printing the results
after each stage of operation: