>I have create a student rank.dbf with five fields namely 1. English 2. Maths 3. Science 4. Total marks 5. Rank.
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>I want to put the Rank for each student based on their Total marks secured.The total marks is out of 500.
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>For example student A secured total marks is 489 out of 500 and student B is 492 and student C is 389 and student D is 391.
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>The Rank for Student B is 1 and student A is 2 and student D is 3 and student C is 4.
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>How to Write source code?

Maybe:

INDEX ON SCORE TAG SCORE DESC
m.i = 1
m.score = SCORE
SCAN
	IF SCORE < m.score
		m.score = SCORE
		i = i+1
	ENDIF
	REPLACE rank WITH i
ENDSCAN