What is the algorithm used to add breakpoints to debug a code? For example a code of 1000 lines where and how many breakpoints should I add

Breakpoints break (temporarily halt) execution of a program during runtime at certain point.

Breakpoints is a feature provided by the debugger in Microsoft Visual Studio that allows breaking execution of code at runtime when debugging applications.For Example

When you click on the side (in the margin) of a line of code in Visual Studio it sets a break point in your code as displayed in the image above. So when you start execution (debug) the code it will break execution at this point. BreakPoint Menu (Option for the Break)he precediing image shows the context-menu for breakpoints, in other words the breakpoint menu. The following describes all the options one by one.

1. Delete BreakpointThis option of the breakpoint menu allows removal of a breakpoint. 
2. Disable BreakpointThis option of the breakpoint menu allows disabling a breakpoint so the breakpoint is just disabled and becomes gray. This is useful when the developer just wants to execute code without stopping at the breakpoint yet later on enable it again when they want to use it again. 
3. Location…This menu option allows setting a breakpoint at a specified location, in other words at a given line in the source code file.

As the name suggest it should be placed where you want to stop the execution of software/application under debugging. I am not if there is any rule of thumb exists for deciding where to put the breakpoint while debugging it merely depends on programmer/reviewer of the code.

C++ using Visual Studio, Java with Eclipse