My First make file which works

# Define required macros here
SHELL = /bin/sh

CFLAG = -Wall -g
CC = gfortran
INCLUDE =
LIBS = -lm

# Write program dependency and main program

SRCS = SubProg1.f90 SubProg2.f90 SubProg3.f90 SubProg4.f90 SubProg5.f90 SubProg6.f90 MainProg.f90

OBJS = $(SRCS:.c=.mod)

MAIN= MainProg

.PHONY: depend clean

all:$(MAIN)
@echo  Simple compiler named mycc has been compiled

$(MAIN): $(OBJS)
$(CC) $(CFLAGS) $(INCLUDES) -o $(MAIN) $(OBJS) $(LFLAGS) $(LIBS)

.c.o:
$(CC) $(CFLAGS) $(INCLUDES) -c $<  -o $@

clean:
$(RM) *.mod *~ $(MAIN)

depend: $(SRCS)
makedepend $(INCLUDES) $^

Not so frequently used keywords c++

alignas, alignof, and_eq, asm, auto, bitand, bitor, catch, char16_t, char32_t, compl,  constexpr, const_cast, decltype, dynamic_cast, enum, explicit, export, inline, mutable,  noexcept, not_eq, nullptr, operator, or_eq, protected, register, reinterpret_cast, short, signed, sizeof, static_assert, static_cast, template, this, thread_local, throw, try,  typeid, typename, union, unsigned, using, virtual, volatile, wchar_t, xor, xor_eq


Very important: The C++ language is a "case sensitive" language. 

Storage classes

The storage for variables with global or namespace scope is allocated for the entire duration of the program. This is known as static storage, and it contrasts with the storage for local variables (those declared within a block). These use what is known as automatic storage. The storage for local variables is only available during the block in which they are declared; after that, that same storage may be used for a local variable of some other function, or used otherwise.

But there is another substantial difference between variables with static storage and variables with automatic storage:
- Variables with static storage (such as global variables) that are not explicitly initialized are automatically initialized to zeroes.
- Variables with automatic storage (such as local variables) that are not explicitly initialized are left uninitialized, and thus have an undetermined value.


Source: C++ tutorial

Change terminal work place to look like [02:43:14]/h/r/Desktop:

PROMPT_COMMAND='pwd2=$(sed "s:\([^/]\)[^/]*/:\1/:g" <<<$PWD)'
export PS1='\[\033[1;35m\][\t]\[\033[1;33m\]$pwd2\[\033[1;36m\]: '


Put the above two lines in the .bashrc file and re-login. Change \numbers to edit the colour.

Checks column 2, 3 and 4 for any -ve value, and replaces it by +ve.

awk '{print $1, $2<0?$2*-1:$2, $3<0?$3*-1:$3, $4<0?$4*-1:$4}' file1 > file2

awk '{ print $1,"\t" $2*10}' file.in > file.out

Multiply column 2 by 10.

sed -n '0~10p' file.in > file.out

To copy every 10th row, starting from 0th row, from a file file.in to file.out

Reduce the size of an image.

identify name1.file name2.file  #.... (This will give the details of files.)
convert in.file -resize n out.file # (converts infile to outfile of size n x n+dn )