just overciew of High Level Designing and Low Level Designing..

2. HLD
In high level designing the overall project will be divided into modules...........
LLD
in low level desiginng the modules are divided into sub modules
and the acutal coding will be done....

3. HLD In Brief
Based on SRS software analysts will convert the requirements into a
usable product. They will design an application which will help the
programmers in coding.In the design process the product is to be
broken into independent modules and then taking each module
at a time and then further breaking them to arrive at micro levels
The HLD document contains the following items at a macro level: -
list of modules and a brief description of each module –
brief functionality of each module - interface relationship among
modules -dependencies between modules - database tables
identified along with key elements - overall architecture diagrams
along with technology details.

4. LLD In Brief
System analysts prepare a micro level design document
called LLD. This document describes each and every module
in an elaborate manner so that the programmer can directly
code the program based on this. There will be at least 1
document for each module and there may be more for a
module.The LLD will contain: - deailed functional logic of
the module in pseudo code - database tables with all
elements including their type and size - all interface
details with complete API references(both requests and
responses) - all dependency issues -error message listings -
complete input and outputs for a module.