第十讲 编程.ppt

* * Lecture 4 程序 主讲：王永龙 临 沂 大 学 理 学 院 主要内容 2.顺序结构 3. 分支结构 4. 顺序结构 1.关系和逻辑运算符 5. 函数编写 3. 分支结构 (1) if 结构 % Script file: calc_roots_quad.m % %Purpose: % This program solves the roots of a %quadratic equation with the form %a*x^2+b*x+c=0, whether the roots are two %distinct real roots, two identical real roots, or %two complex roots. % %Records of revisions: %Date 2007-11-11 %Programmer: Wang Yong-Long %Description of change: original code % %Define variables: %a: coefficient of x^2 term of the equation %b: coefficient of x term of the equation %c: the constant term of the equation %s: discriminant (判别式) of the equation %image: the image part of the root %real: the real part of the root %x1: First root of the equation %x2: Second root of the equation. % %Prompt the user to enter the coefficients of %the equation disp(‘This program solves the roots of the quadratic’); disp(‘equation with the form a*x^2+b*x+c=0’); a=input(‘Enter the coefficient a: ‘); b=input(‘Enter the coefficient b: ‘); c=input(‘Enter the coefficient c: ‘); %Calculate the discriminant of the equation s=b^2-4*a*c; % %Solve the roots, depending on the value of the % discriminant s. if s0 %There are two real roots. x1=(-b-sqrt(s))/(2*a); x2=(-b+sqrt(s)/(2*a); disp(‘This equation has two real roots as:’) fprintf(‘x1=%f\n’,x1); fprintf(‘x2=%f\n’,x2); elseif s==0 %There are only single repeated real root. x1=(-b)/(2*a); disp(‘This equation has a single repeated root (two identical real roots) as:’); fprintf(‘x1=x2=%f\n’,x1); else %There are two complex roots. real=-b/(2*a); image=(sqrt(abs(s)))/(2*a); disp(‘This equation has two complex roots:’); fprintf(‘x1=%f-i*%f\n’, real, image); fprintf(‘x2=%f+i*%f\n’, real, image) end (2) switch 结构 编写一程序能够根据输入的学生成绩给出恰当评述。学生成绩分为五个等级：A (或 a), B (或 b), C (或 c), D (或 d), 和E (或 e)。根据这些等级，给出恰当评述。 % Script file: stud_subj_eval.m % % Purpose: %This program shows the record of %corresponding stude