AND and OR in IF statement in linux script

#var1
abc=0
# $1 is ist argument
echo -en "1st arg $1 and $abc\n"

# OR of two expr
if [ "$1" = "vikas" -o $abc -eq 1 ] ; then
echo "true"
else
echo "false"
fi

# AND of two expr
if [ "$1" = "vikas" -a $abc -eq 1 ] ; then
echo "true"
else
echo "false"
fi